<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
<!--Created by Vintage Filings ("VF")-->
<!--produced on 2014-05-14 @ 1:45 PM-->
<link:linkbase xmlns:isr="http://www.isoray.com/20140331" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase">
  <link:roleRef roleURI="http://www.isoray.com/role/BasisOfPresentation" xlink:href="isr-20140331.xsd#isr-bop" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/BasisOfPresentationDetails" xlink:href="isr-20140331.xsd#isr-bopd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/CommitmentsAndContingencies" xlink:href="isr-20140331.xsd#isr-cac" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/CommitmentsAndContingenciesDetails" xlink:href="isr-20140331.xsd#isr-cacd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ConsolidatedBalanceSheets" xlink:href="isr-20140331.xsd#isr-cbs" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:href="isr-20140331.xsd#isr-cbsp" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="isr-20140331.xsd#isr-csocf" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ConsolidatedStatementsOfOperations" xlink:href="isr-20140331.xsd#isr-csoo" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/DocumentAndEntityInformation" xlink:href="isr-20140331.xsd#isr-daei" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/FairValueMeasurements" xlink:href="isr-20140331.xsd#isr-fvm" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/FairValueMeasurementsDetails" xlink:href="isr-20140331.xsd#isr-fvmd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/FairValueMeasurementsTables" xlink:href="isr-20140331.xsd#isr-fvmt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/InventoryDetails" xlink:href="isr-20140331.xsd#isr-id" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/Inventory" xlink:href="isr-20140331.xsd#isr-i" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/InventoryTables" xlink:href="isr-20140331.xsd#isr-it" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/LossPerShare" xlink:href="isr-20140331.xsd#isr-lps" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/LossPerShareDetails" xlink:href="isr-20140331.xsd#isr-lpsd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/LossPerShareTables" xlink:href="isr-20140331.xsd#isr-lpst" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/NewAccountingPronouncements" xlink:href="isr-20140331.xsd#isr-nap" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/PreferredDividendsDetails" xlink:href="isr-20140331.xsd#isr-pdd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/PreferredDividends" xlink:href="isr-20140331.xsd#isr-pd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/RelatedPartyTransaction" xlink:href="isr-20140331.xsd#isr-rpt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/RelatedPartyTransactionDetails" xlink:href="isr-20140331.xsd#isr-rptd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/SharebasedCompensationTables" xlink:href="isr-20140331.xsd#isr-sct" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/SharebasedCompensation" xlink:href="isr-20140331.xsd#isr-sc" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/SharebasedCompensationScheduleOfSharebasedCompensationExpenseDetails" xlink:href="isr-20140331.xsd#isr-scsosced" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/SharebasedCompensationScheduleOfStockOptionActivityDetails" xlink:href="isr-20140331.xsd#isr-scsosoad" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ShareholdersEquity" xlink:href="isr-20140331.xsd#isr-se" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ShareholdersEquityCommonAndPreferredStockTransactionsDetails" xlink:href="isr-20140331.xsd#isr-secapstd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ShareholdersEquityScheduleOfInputsForFairValueModelDetails" xlink:href="isr-20140331.xsd#isr-sesoiffvmd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ShareholdersEquityTables" xlink:href="isr-20140331.xsd#isr-set" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ShareholdersEquityWarrantsDetails" xlink:href="isr-20140331.xsd#isr-sewd" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/SubsequentEvent" xlink:href="isr-20140331.xsd#isr-se123" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ShareholdersEquityAdditionalInformationAboutWarrantsDetails" xlink:href="isr-20140331.xsd#isr-seaiawd1" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/SubsequentEventDetails" xlink:href="isr-20140331.xsd#isr-sed1" xlink:type="simple" />
  <link:roleRef roleURI="http://www.isoray.com/role/ShareholdersEquityWarrantExercisesDetails" xlink:href="isr-20140331.xsd#isr-sewed" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/notAll" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#notAll" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:definitionLink xlink:title="40601 - Disclosure - Commitments and Contingencies (Details)" xlink:role="http://www.isoray.com/role/CommitmentsAndContingenciesDetails" xlink:type="extended">
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsLineItems.2306.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ScheduleOfFiniteLivedIntangibleAssetsTable.4785.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FiniteLivedIntangibleAssetsLineItems.2306.9.6" xlink:to="loc_ScheduleOfFiniteLivedIntangibleAssetsTable.4785.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsLineItems.2306.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_PercentageOfRoyaltyRatePayableOnNetSales.26094.7.6" xlink:href="isr-20140331.xsd#isr_PercentageOfRoyaltyRatePayableOnNetSales" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FiniteLivedIntangibleAssetsLineItems.2306.7.6" xlink:to="loc_PercentageOfRoyaltyRatePayableOnNetSales.26094.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsMajorClassNameDomain.2309.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_PatentRightsKnowhowAndLicenseAgreementsMember.26089.7.6" xlink:href="isr-20140331.xsd#isr_PatentRightsKnowhowAndLicenseAgreementsMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FiniteLivedIntangibleAssetsMajorClassNameDomain.2309.7.6" xlink:to="loc_PatentRightsKnowhowAndLicenseAgreementsMember.26089.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsByMajorClassAxis.2311.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsMajorClassNameDomain.2309.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FiniteLivedIntangibleAssetsByMajorClassAxis.2311.8.6" xlink:to="loc_FiniteLivedIntangibleAssetsMajorClassNameDomain.2309.8.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsByMajorClassAxis.2311.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsMajorClassNameDomain.2309.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FiniteLivedIntangibleAssetsByMajorClassAxis.2311.6.6" xlink:to="loc_FiniteLivedIntangibleAssetsMajorClassNameDomain.2309.6.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_ScheduleOfFiniteLivedIntangibleAssetsTable.4785.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:type="locator" />
    <link:loc xlink:label="loc_FiniteLivedIntangibleAssetsByMajorClassAxis.2311.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ScheduleOfFiniteLivedIntangibleAssetsTable.4785.5.6" xlink:to="loc_FiniteLivedIntangibleAssetsByMajorClassAxis.2311.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="002 - Statement - Consolidated Balance Sheets" xlink:role="http://www.isoray.com/role/ConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:label="loc_AssetsCurrentAbstract.616.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:type="locator" />
    <link:loc xlink:label="loc_CashAndCashEquivalentsAtCarryingValue.6843.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsCurrentAbstract.616.7.6" xlink:to="loc_CashAndCashEquivalentsAtCarryingValue.6843.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AccountsReceivableNetCurrent.5665.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsCurrentAbstract.616.7.6" xlink:to="loc_AccountsReceivableNetCurrent.5665.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_InventoryNet.11816.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_InventoryNet" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsCurrentAbstract.616.7.6" xlink:to="loc_InventoryNet.11816.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PrepaidExpenseAndOtherAssetsCurrent.14776.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsCurrentAbstract.616.7.6" xlink:to="loc_PrepaidExpenseAndOtherAssetsCurrent.14776.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AssetsCurrent.6084.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetsCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsCurrentAbstract.616.7.6" xlink:to="loc_AssetsCurrent.6084.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AssetsAbstract.620.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetsAbstract" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsAbstract.620.7.6" xlink:to="loc_AssetsCurrentAbstract.616.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PropertyPlantAndEquipmentNet.15211.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsAbstract.620.7.6" xlink:to="loc_PropertyPlantAndEquipmentNet.15211.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RestrictedCashAndCashEquivalentsNoncurrent.15932.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsNoncurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsAbstract.620.7.6" xlink:to="loc_RestrictedCashAndCashEquivalentsNoncurrent.15932.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_InventoryNoncurrent.11871.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_InventoryNoncurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsAbstract.620.7.6" xlink:to="loc_InventoryNoncurrent.11871.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_OtherAssetsNoncurrent.13824.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsAbstract.620.7.6" xlink:to="loc_OtherAssetsNoncurrent.13824.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_Assets.6057.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_Assets" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsAbstract.620.7.6" xlink:to="loc_Assets.6057.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_SeriesAPreferredStockMember.5023.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesAPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesAPreferredStockMember.5023.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesBPreferredStockMember.5029.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesBPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesBPreferredStockMember.5029.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesCPreferredStockMember.5028.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesCPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesCPreferredStockMember.5028.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_LiabilitiesCurrentAbstract.3060.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:type="locator" />
    <link:loc xlink:label="loc_AccountsPayableAndAccruedLiabilitiesCurrent.5646.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesCurrentAbstract.3060.7.6" xlink:to="loc_AccountsPayableAndAccruedLiabilitiesCurrent.5646.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_OtherLiabilitiesCurrent.14014.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OtherLiabilitiesCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesCurrentAbstract.3060.7.6" xlink:to="loc_OtherLiabilitiesCurrent.14014.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_EmployeeRelatedLiabilitiesCurrent.9197.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesCurrentAbstract.3060.7.6" xlink:to="loc_EmployeeRelatedLiabilitiesCurrent.9197.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AccruedVacationCurrent.5736.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccruedVacationCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesCurrentAbstract.3060.7.6" xlink:to="loc_AccruedVacationCurrent.5736.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_LiabilitiesCurrent.12126.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesCurrentAbstract.3060.7.6" xlink:to="loc_LiabilitiesCurrent.12126.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_OtherAccruedLiabilitiesCurrent.14070.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesCurrentAbstract.3060.7.6" xlink:to="loc_OtherAccruedLiabilitiesCurrent.14070.7.6" order="1.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:to="loc_LiabilitiesCurrentAbstract.3060.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_DerivativeLiabilitiesNoncurrent.8356.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DerivativeLiabilitiesNoncurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:to="loc_DerivativeLiabilitiesNoncurrent.8356.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AssetRetirementObligationsNoncurrent.6027.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetRetirementObligationsNoncurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:to="loc_AssetRetirementObligationsNoncurrent.6027.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_Liabilities.12166.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_Liabilities" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:to="loc_Liabilities.12166.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_CommitmentsAndContingencies.7121.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:to="loc_CommitmentsAndContingencies.7121.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StockholdersEquityAbstract.5197.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:to="loc_StockholdersEquityAbstract.5197.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_LiabilitiesAndStockholdersEquity.12135.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" xlink:to="loc_LiabilitiesAndStockholdersEquity.12135.7.6" order="7.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementTable.5163.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:type="locator" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementTable.5163.5.6" xlink:to="loc_StatementClassOfStockAxis.5173.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementLineItems.5164.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_StatementTable.5163.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.9.6" xlink:to="loc_StatementTable.5163.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesDPreferredStockMember.5026.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesDPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesDPreferredStockMember.5026.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementLineItems.5164.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_AssetsAbstract.620.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_LiabilitiesAndStockholdersEquityAbstract.3066.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.8.6" xlink:to="loc_ClassOfStockDomain.1024.8.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.6.6" xlink:to="loc_ClassOfStockDomain.1024.6.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredStockValue.14687.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockValue" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StockholdersEquityAbstract.5197.7.6" xlink:to="loc_PreferredStockValue.14687.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_CommonStockValue.7134.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockValue" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StockholdersEquityAbstract.5197.7.6" xlink:to="loc_CommonStockValue.7134.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_TreasuryStockValue.17716.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TreasuryStockValue" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StockholdersEquityAbstract.5197.7.6" xlink:to="loc_TreasuryStockValue.17716.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AdditionalPaidInCapital.5816.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StockholdersEquityAbstract.5197.7.6" xlink:to="loc_AdditionalPaidInCapital.5816.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RetainedEarningsAccumulatedDeficit.16058.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StockholdersEquityAbstract.5197.7.6" xlink:to="loc_RetainedEarningsAccumulatedDeficit.16058.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StockholdersEquity.17302.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockholdersEquity" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StockholdersEquityAbstract.5197.7.6" xlink:to="loc_StockholdersEquity.17302.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="003 - Statement - Consolidated Balance Sheets (Parenthetical)" xlink:role="http://www.isoray.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_SeriesAPreferredStockMember.5023.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesAPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesAPreferredStockMember.5023.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesBPreferredStockMember.5029.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesBPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesBPreferredStockMember.5029.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesCPreferredStockMember.5028.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesCPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesCPreferredStockMember.5028.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementTable.5163.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:type="locator" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementTable.5163.5.6" xlink:to="loc_StatementClassOfStockAxis.5173.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementLineItems.5164.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_StatementTable.5163.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.9.6" xlink:to="loc_StatementTable.5163.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesDPreferredStockMember.5026.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesDPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesDPreferredStockMember.5026.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementLineItems.5164.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_AllowanceForDoubtfulAccountsReceivableCurrent.5921.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_AllowanceForDoubtfulAccountsReceivableCurrent.5921.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredStockParOrStatedValuePerShare.14668.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_PreferredStockParOrStatedValuePerShare.14668.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredStockSharesAuthorized.14701.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_PreferredStockSharesAuthorized.14701.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredStockSharesIssued.14694.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_PreferredStockSharesIssued.14694.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredStockSharesOutstanding.14710.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_PreferredStockSharesOutstanding.14710.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_CommonStockParOrStatedValuePerShare.7131.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_CommonStockParOrStatedValuePerShare.7131.7.6" order="7.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_CommonStockSharesAuthorized.7144.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_CommonStockSharesAuthorized.7144.7.6" order="8.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_CommonStockSharesIssued.7136.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_CommonStockSharesIssued.7136.7.6" order="9.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_CommonStockSharesOutstanding.7164.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_CommonStockSharesOutstanding.7164.7.6" order="10.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_TreasuryStockShares.17707.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_TreasuryStockShares" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementLineItems.5164.7.6" xlink:to="loc_TreasuryStockShares.17707.7.6" order="11.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.8.6" xlink:to="loc_ClassOfStockDomain.1024.8.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.6.6" xlink:to="loc_ClassOfStockDomain.1024.6.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40701 - Disclosure - Fair Value Measurements (Details)" xlink:role="http://www.isoray.com/role/FairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:label="loc_AssetsFairValueDisclosureAbstract.608.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AssetsFairValueDisclosureAbstract" xlink:type="locator" />
    <link:loc xlink:label="loc_CashAndCashEquivalentsFairValueDisclosure.6850.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsFairValueDisclosureAbstract.608.7.6" xlink:to="loc_CashAndCashEquivalentsFairValueDisclosure.6850.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RestrictedCashAndCashEquivalents.15914.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalents" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsFairValueDisclosureAbstract.608.7.6" xlink:to="loc_RestrictedCashAndCashEquivalents.15914.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AccountsReceivableFairValueDisclosure.5649.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AccountsReceivableFairValueDisclosure" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AssetsFairValueDisclosureAbstract.608.7.6" xlink:to="loc_AccountsReceivableFairValueDisclosure.5649.7.6" order="1.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueByMeasurementFrequencyAxis.1988.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueMeasurementFrequencyDomain.2021.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueByMeasurementFrequencyAxis.1988.6.6" xlink:to="loc_FairValueMeasurementFrequencyDomain.2021.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueByMeasurementFrequencyAxis.1988.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueMeasurementFrequencyDomain.2021.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueByMeasurementFrequencyAxis.1988.8.6" xlink:to="loc_FairValueMeasurementFrequencyDomain.2021.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable.1996.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueByFairValueHierarchyLevelAxis.1998.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable.1996.5.6" xlink:to="loc_FairValueByFairValueHierarchyLevelAxis.1998.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueByFairValueHierarchyLevelAxis.1998.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueMeasurementsFairValueHierarchyDomain.2060.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueByFairValueHierarchyLevelAxis.1998.8.6" xlink:to="loc_FairValueMeasurementsFairValueHierarchyDomain.2060.8.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueByFairValueHierarchyLevelAxis.1998.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueMeasurementsFairValueHierarchyDomain.2060.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueByFairValueHierarchyLevelAxis.1998.6.6" xlink:to="loc_FairValueMeasurementsFairValueHierarchyDomain.2060.6.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueMeasurementFrequencyDomain.2021.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueMeasurementsRecurringMember.2011.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueMeasurementFrequencyDomain.2021.7.6" xlink:to="loc_FairValueMeasurementsRecurringMember.2011.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueByMeasurementFrequencyAxis.1988.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable.1996.5.6" xlink:to="loc_FairValueByMeasurementFrequencyAxis.1988.5.6" order="1.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueMeasurementsFairValueHierarchyDomain.2060.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueInputsLevel1Member.2138.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueMeasurementsFairValueHierarchyDomain.2060.7.6" xlink:to="loc_FairValueInputsLevel1Member.2138.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems.2051.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable.1996.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems.2051.9.6" xlink:to="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable.1996.9.6" order="2.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems.2051.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems.2051.7.6" xlink:to="loc_AssetsFairValueDisclosureAbstract.608.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_LiabilitiesFairValueDisclosureAbstract.3067.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems.2051.7.6" xlink:to="loc_LiabilitiesFairValueDisclosureAbstract.3067.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_FairValueInputsLevel2Member.2139.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_FairValueMeasurementsFairValueHierarchyDomain.2060.7.6" xlink:to="loc_FairValueInputsLevel2Member.2139.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_DerivativeLiabilities.8379.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_LiabilitiesFairValueDisclosureAbstract.3067.7.6" xlink:to="loc_DerivativeLiabilities.8379.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40301 - Disclosure - Loss per Share (Details)" xlink:role="http://www.isoray.com/role/LossPerShareDetails" xlink:type="extended">
    <link:loc xlink:label="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis.579.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesNameDomain.582.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis.579.8.6" xlink:to="loc_AntidilutiveSecuritiesNameDomain.582.8.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis.579.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesNameDomain.582.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis.579.6.6" xlink:to="loc_AntidilutiveSecuritiesNameDomain.582.6.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems.581.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable.4777.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems.581.9.6" xlink:to="loc_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable.4777.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems.581.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount.6016.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems.581.7.6" xlink:to="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount.6016.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesNameDomain.582.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_WarrantMember.5560.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_WarrantMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesNameDomain.582.7.6" xlink:to="loc_WarrantMember.5560.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_EmployeeStockOptionMember.1806.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesNameDomain.582.7.6" xlink:to="loc_EmployeeStockOptionMember.1806.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable.4777.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:type="locator" />
    <link:loc xlink:label="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis.579.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable.4777.5.6" xlink:to="loc_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis.579.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesBPreferredStockMember.5029.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesBPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesNameDomain.582.7.6" xlink:to="loc_SeriesBPreferredStockMember.5029.7.6" order="1.25000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesDPreferredStockMember.5026.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesDPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_AntidilutiveSecuritiesNameDomain.582.7.6" xlink:to="loc_SeriesDPreferredStockMember.5026.7.6" order="1.62500" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40801 - Disclosure - Preferred Dividends (Details)" xlink:role="http://www.isoray.com/role/PreferredDividendsDetails" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_SeriesBPreferredStockMember.5029.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesBPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesBPreferredStockMember.5029.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_DividendsPayableTable.1689.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsPayableTable" xlink:type="locator" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_DividendsPayableTable.1689.5.6" xlink:to="loc_StatementClassOfStockAxis.5173.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_DividendsPayableLineItems.1695.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsPayableLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_DividendsPayableTable.1689.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsPayableTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_DividendsPayableLineItems.1695.9.6" xlink:to="loc_DividendsPayableTable.1689.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_DividendsPayableLineItems.1695.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsPayableLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_DividendsPayableDateDeclaredDayMonthAndYear.9017.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_DividendsPayableLineItems.1695.7.6" xlink:to="loc_DividendsPayableDateDeclaredDayMonthAndYear.9017.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredStockAmountOfPreferredDividendsInArrears.14693.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockAmountOfPreferredDividendsInArrears" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_DividendsPayableLineItems.1695.7.6" xlink:to="loc_PreferredStockAmountOfPreferredDividendsInArrears.14693.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PaymentsOfDividendsPreferredStockAndPreferenceStock.14313.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStock" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_DividendsPayableLineItems.1695.7.6" xlink:to="loc_PaymentsOfDividendsPreferredStockAndPreferenceStock.14313.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.8.6" xlink:to="loc_ClassOfStockDomain.1024.8.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.6.6" xlink:to="loc_ClassOfStockDomain.1024.6.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_DividendsPreferredStock.9020.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_DividendsPreferredStock" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_DividendsPayableLineItems.1695.7.6" xlink:to="loc_DividendsPreferredStock.9020.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="41001 - Disclosure - Related Party Transaction (Details)" xlink:role="http://www.isoray.com/role/RelatedPartyTransactionDetails" xlink:type="extended">
    <link:loc xlink:label="loc_RelatedPartyTransactionLineItems.4538.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable.4873.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_RelatedPartyTransactionLineItems.4538.9.6" xlink:to="loc_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable.4873.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_RelatedPartyTransactionLineItems.4538.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty.15775.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_RelatedPartyTransactionLineItems.4538.7.6" xlink:to="loc_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty.15775.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RelatedPartyDomain.4542.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_AffiliatedEntityMember.513.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AffiliatedEntityMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_RelatedPartyDomain.4542.7.6" xlink:to="loc_AffiliatedEntityMember.513.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RelatedPartyTransactionsByRelatedPartyAxis.4540.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_RelatedPartyDomain.4542.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_RelatedPartyTransactionsByRelatedPartyAxis.4540.6.6" xlink:to="loc_RelatedPartyDomain.4542.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_RelatedPartyTransactionsByRelatedPartyAxis.4540.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_RelatedPartyDomain.4542.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_RelatedPartyTransactionsByRelatedPartyAxis.4540.8.6" xlink:to="loc_RelatedPartyDomain.4542.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_CostOfPropertyRepairsAndMaintenance.7388.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CostOfPropertyRepairsAndMaintenance" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_RelatedPartyTransactionLineItems.4538.7.6" xlink:to="loc_CostOfPropertyRepairsAndMaintenance.7388.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable.4873.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:type="locator" />
    <link:loc xlink:label="loc_RelatedPartyTransactionsByRelatedPartyAxis.4540.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable.4873.5.6" xlink:to="loc_RelatedPartyTransactionsByRelatedPartyAxis.4540.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40501 - Disclosure - Share-Based Compensation (Schedule of Share-Based Compensation Expense) (Details)" xlink:role="http://www.isoray.com/role/SharebasedCompensationScheduleOfSharebasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:label="loc_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems.1805.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable.4815.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems.1805.9.6" xlink:to="loc_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable.4815.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems.1805.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions.9215.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems.1805.7.6" xlink:to="loc_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions.9215.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1.9214.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems.1805.7.6" xlink:to="loc_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1.9214.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_AllocatedShareBasedCompensationExpense.5919.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems.1805.7.6" xlink:to="loc_AllocatedShareBasedCompensationExpense.5919.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_IncomeStatementLocationAxis.2652.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_IncomeStatementLocationDomain.2671.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_IncomeStatementLocationAxis.2652.6.6" xlink:to="loc_IncomeStatementLocationDomain.2671.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod.16212.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems.1805.7.6" xlink:to="loc_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod.16212.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable.4815.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:type="locator" />
    <link:loc xlink:label="loc_IncomeStatementLocationAxis.2652.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable.4815.5.6" xlink:to="loc_IncomeStatementLocationAxis.2652.5.6" order="1.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_IncomeStatementLocationAxis.2652.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_IncomeStatementLocationDomain.2671.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_IncomeStatementLocationAxis.2652.8.6" xlink:to="loc_IncomeStatementLocationDomain.2671.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_IncomeStatementLocationDomain.2671.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_CostOfSalesMember.1254.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CostOfSalesMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_IncomeStatementLocationDomain.2671.7.6" xlink:to="loc_CostOfSalesMember.1254.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ResearchAndDevelopmentExpenseMember.4573.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_IncomeStatementLocationDomain.2671.7.6" xlink:to="loc_ResearchAndDevelopmentExpenseMember.4573.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SellingAndMarketingExpenseMember.5005.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SellingAndMarketingExpenseMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_IncomeStatementLocationDomain.2671.7.6" xlink:to="loc_SellingAndMarketingExpenseMember.5005.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_GeneralAndAdministrativeExpenseMember.2476.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_IncomeStatementLocationDomain.2671.7.6" xlink:to="loc_GeneralAndAdministrativeExpenseMember.2476.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40901 - Disclosure - Shareholders' Equity (Common and Preferred Stock Transactions) (Details)" xlink:role="http://www.isoray.com/role/ShareholdersEquityCommonAndPreferredStockTransactionsDetails" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfStockLineItems.1018.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_GrossProceedsFromIssuanceOfStock.26086.7.6" xlink:href="isr-20140331.xsd#isr_GrossProceedsFromIssuanceOfStock" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_GrossProceedsFromIssuanceOfStock.26086.7.6" order="10.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PaymentsOfStockIssuanceCostsCommissionExpense.26090.7.6" xlink:href="isr-20140331.xsd#isr_PaymentsOfStockIssuanceCostsCommissionExpense" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_PaymentsOfStockIssuanceCostsCommissionExpense.26090.7.6" order="12.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PaymentsOfStockIssuanceCostsLegalAndAccountingExpense.26091.7.6" xlink:href="isr-20140331.xsd#isr_PaymentsOfStockIssuanceCostsLegalAndAccountingExpense" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_PaymentsOfStockIssuanceCostsLegalAndAccountingExpense.26091.7.6" order="13.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PaymentsOfStockIssuanceCostsListingExpense.26092.7.6" xlink:href="isr-20140331.xsd#isr_PaymentsOfStockIssuanceCostsListingExpense" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_PaymentsOfStockIssuanceCostsListingExpense.26092.7.6" order="14.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PaymentsOfStockIssuanceCostsOtherExpenses.26093.7.6" xlink:href="isr-20140331.xsd#isr_PaymentsOfStockIssuanceCostsOtherExpenses" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_PaymentsOfStockIssuanceCostsOtherExpenses.26093.7.6" order="16.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfStockLineItems.1018.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ScheduleOfStockByClassTable.4895.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.9.6" xlink:to="loc_ScheduleOfStockByClassTable.4895.9.6" order="18.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_ProceedsFromIssuanceOrSaleOfEquity.14962.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ProceedsFromIssuanceOrSaleOfEquity.14962.7.6" order="20.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PaymentsForUnderwritingFeesCosts.32379.7.6" xlink:href="isr-20140331.xsd#isr_PaymentsForUnderwritingFeesCosts" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_PaymentsForUnderwritingFeesCosts.32379.7.6" order="11.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StockIssuedDuringPeriodSharesNewIssues.17271.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_StockIssuedDuringPeriodSharesNewIssues.17271.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight.7038.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight.7038.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights.7036.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights.7036.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SharesIssuedPricePerShare.17055.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_SharesIssuedPricePerShare.17055.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTerm.32382.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightTerm" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ClassOfWarrantOrRightTerm.32382.7.6" order="7.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_CommonStockMember.1087.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_CommonStockMember.1087.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ScheduleOfStockByClassTable.4895.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:type="locator" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ScheduleOfStockByClassTable.4895.5.6" xlink:to="loc_StatementClassOfStockAxis.5173.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.6.6" xlink:to="loc_ClassOfStockDomain.1024.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.8.6" xlink:to="loc_ClassOfStockDomain.1024.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_CommonUnitWarrantsMember.32380.7.6" xlink:href="isr-20140331.xsd#isr_CommonUnitWarrantsMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_CommonUnitWarrantsMember.32380.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesDPreferredStockMember.5026.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesDPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesDPreferredStockMember.5026.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ScheduleOfStockByClassTable.4895.5.6" xlink:to="loc_ClassOfWarrantOrRightAxis.1019.5.6" order="1.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredUnitWarrantsMember.32381.7.6" xlink:href="isr-20140331.xsd#isr_PreferredUnitWarrantsMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_PreferredUnitWarrantsMember.32381.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ConvertiblePreferredStockMaximumOwnershipInterest.32383.7.6" xlink:href="isr-20140331.xsd#isr_ConvertiblePreferredStockMaximumOwnershipInterest" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ConvertiblePreferredStockMaximumOwnershipInterest.32383.7.6" order="9.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ConvertiblePreferredStockSharesIssuedUponConversion.7359.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConvertiblePreferredStockSharesIssuedUponConversion" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ConvertiblePreferredStockSharesIssuedUponConversion.7359.7.6" order="8.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_PreferredStockRedemptionPremium.14691.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_PreferredStockRedemptionPremium" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_PreferredStockRedemptionPremium.14691.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ConversionOfStockSharesConverted1.7346.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConversionOfStockSharesConverted1" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ConversionOfStockSharesConverted1.7346.7.6" order="15.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ConversionOfStockSharesIssued1.7335.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ConversionOfStockSharesIssued1" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_ConversionOfStockSharesIssued1.7335.7.6" order="17.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_CommonStockSharesOutstanding.7164.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockLineItems.1018.7.6" xlink:to="loc_CommonStockSharesOutstanding.7164.7.6" order="19.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40904 - Disclosure - Shareholders' Equity (Schedule of Inputs for Fair Value Model) (Details)" xlink:role="http://www.isoray.com/role/ShareholdersEquityScheduleOfInputsForFairValueModelDetails" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:to="loc_ClassOfWarrantOrRightTable.1025.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightOutstanding.7031.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightOutstanding" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightOutstanding.7031.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_CommonStockPurchaserWarrantsMember.26097.7.6" xlink:href="isr-20140331.xsd#isr_CommonStockPurchaserWarrantsMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_CommonStockPurchaserWarrantsMember.26097.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_OverAllotmentWarrantsMember.26106.7.6" xlink:href="isr-20140331.xsd#isr_OverAllotmentWarrantsMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_OverAllotmentWarrantsMember.26106.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:to="loc_ClassOfWarrantOrRightAxis.1019.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsValueAbstract.26107.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsValueAbstract" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_WarrantsValueAbstract.26107.7.6" order="9.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsAndRightsOutstanding.18000.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_WarrantsAndRightsOutstanding" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_WarrantsValueAbstract.26107.7.6" xlink:to="loc_WarrantsAndRightsOutstanding.18000.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_UnrealizedGainLossOnDerivatives.17811.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_WarrantsValueAbstract.26107.7.6" xlink:to="loc_UnrealizedGainLossOnDerivatives.17811.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares.26087.7.6" xlink:href="isr-20140331.xsd#isr_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares.26087.7.6" order="1.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightCorrected.49720.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightCorrected" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightCorrected.49720.7.6" order="1.30000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsAndRightsCorrected.49731.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsAndRightsCorrected" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_WarrantsValueAbstract.26107.7.6" xlink:to="loc_WarrantsAndRightsCorrected.49731.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsAndRightsExercised.49730.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsAndRightsExercised" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_WarrantsValueAbstract.26107.7.6" xlink:to="loc_WarrantsAndRightsExercised.49730.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40905 - Disclosure - Shareholders' Equity (Warrants) (Details)" xlink:role="http://www.isoray.com/role/ShareholdersEquityWarrantsDetails" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightOutstandingAbstract.26082.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightOutstandingAbstract" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightOutstandingAbstract.26082.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightWeightedAverageExercisePriceAbstract.26083.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightWeightedAverageExercisePriceAbstract" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightWeightedAverageExercisePriceAbstract.26083.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:to="loc_ClassOfWarrantOrRightTable.1025.9.6" order="5.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassCWarrantsMember.26080.7.6" xlink:href="isr-20140331.xsd#isr_ClassCWarrantsMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_ClassCWarrantsMember.26080.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:to="loc_ClassOfWarrantOrRightAxis.1019.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightOutstanding.7031.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightOutstanding" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightOutstandingAbstract.26082.7.6" xlink:to="loc_ClassOfWarrantOrRightOutstanding.7031.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightIssuedInPeriodExercisePriceOfWarrantsOrRights.26081.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightIssuedInPeriodExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightWeightedAverageExercisePriceAbstract.26083.7.6" xlink:to="loc_ClassOfWarrantOrRightIssuedInPeriodExercisePriceOfWarrantsOrRights.26081.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightWeightedAverageExercisePriceAbstract.26083.7.6" xlink:to="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" order="0.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightIssued.32390.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightIssued" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightOutstandingAbstract.26082.7.6" xlink:to="loc_ClassOfWarrantOrRightIssued.32390.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightCorrectedInPeriodExercisePriceOfWarrantsOrRights.49722.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightCorrectedInPeriodExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightWeightedAverageExercisePriceAbstract.26083.7.6" xlink:to="loc_ClassOfWarrantOrRightCorrectedInPeriodExercisePriceOfWarrantsOrRights.49722.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightCorrected.49720.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightCorrected" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightOutstandingAbstract.26082.7.6" xlink:to="loc_ClassOfWarrantOrRightCorrected.49720.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares.26087.7.6" xlink:href="isr-20140331.xsd#isr_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightOutstandingAbstract.26082.7.6" xlink:to="loc_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares.26087.7.6" order="3.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightExercisedInPeriodExercisePriceOfWarrantsOrRights.49723.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightExercisedInPeriodExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightWeightedAverageExercisePriceAbstract.26083.7.6" xlink:to="loc_ClassOfWarrantOrRightExercisedInPeriodExercisePriceOfWarrantsOrRights.49723.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40906 - Disclosure - Shareholders' Equity (Additional Information about Warrants) (Details)" xlink:role="http://www.isoray.com/role/ShareholdersEquityAdditionalInformationAboutWarrantsDetails" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_RangeOfExercisePriceOneMember.42652.7.6" xlink:href="isr-20140331.xsd#isr_RangeOfExercisePriceOneMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_RangeOfExercisePriceOneMember.42652.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RangeOfExercisePriceTwoMember.42653.7.6" xlink:href="isr-20140331.xsd#isr_RangeOfExercisePriceTwoMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_RangeOfExercisePriceTwoMember.42653.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RangeOfExercisePriceThreeMember.42654.7.6" xlink:href="isr-20140331.xsd#isr_RangeOfExercisePriceThreeMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_RangeOfExercisePriceThreeMember.42654.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RangeOfExercisePriceFourMember.42655.7.6" xlink:href="isr-20140331.xsd#isr_RangeOfExercisePriceFourMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_RangeOfExercisePriceFourMember.42655.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:to="loc_ClassOfWarrantOrRightTable.1025.9.6" order="3.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightOutstanding.7031.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightOutstanding" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightOutstanding.7031.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" order="4.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsExpirationDate.42651.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsExpirationDate" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_WarrantsExpirationDate.42651.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:to="loc_ClassOfWarrantOrRightAxis.1019.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_RangeOfExercisePriceFiveMember.42656.7.6" xlink:href="isr-20140331.xsd#isr_RangeOfExercisePriceFiveMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_RangeOfExercisePriceFiveMember.42656.7.6" order="5.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RangeOfExercisePriceSixMember.42657.7.6" xlink:href="isr-20140331.xsd#isr_RangeOfExercisePriceSixMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_RangeOfExercisePriceSixMember.42657.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_RangeOfExercisePriceSevenMember.42658.7.6" xlink:href="isr-20140331.xsd#isr_RangeOfExercisePriceSevenMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_RangeOfExercisePriceSevenMember.42658.7.6" order="7.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="41101 - Disclosure - Subsequent Event (Details)" xlink:role="http://www.isoray.com/role/SubsequentEventDetails" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_CommonStockMember.1087.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_CommonStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_CommonStockMember.1087.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SeriesDPreferredStockMember.5026.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SeriesDPreferredStockMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfStockDomain.1024.7.6" xlink:to="loc_SeriesDPreferredStockMember.5026.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.6.6" xlink:to="loc_ClassOfStockDomain.1024.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfStockDomain.1024.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_StatementClassOfStockAxis.5173.8.6" xlink:to="loc_ClassOfStockDomain.1024.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_SubsequentEventTable.5216.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTable" xlink:type="locator" />
    <link:loc xlink:label="loc_SubsequentEventTypeAxis.5220.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_SubsequentEventTable.5216.5.6" xlink:to="loc_SubsequentEventTypeAxis.5220.5.6" order="1.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_StatementClassOfStockAxis.5173.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_SubsequentEventTable.5216.5.6" xlink:to="loc_StatementClassOfStockAxis.5173.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_SubsequentEventTypeAxis.5220.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_SubsequentEventTypeDomain.5219.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_SubsequentEventTypeAxis.5220.8.6" xlink:to="loc_SubsequentEventTypeDomain.5219.8.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_SubsequentEventTypeAxis.5220.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_SubsequentEventTypeDomain.5219.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_SubsequentEventTypeAxis.5220.6.6" xlink:to="loc_SubsequentEventTypeDomain.5219.6.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_SubsequentEventTypeDomain.5219.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_SubsequentEventMember.5218.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_SubsequentEventTypeDomain.5219.7.6" xlink:to="loc_SubsequentEventMember.5218.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_SubsequentEventLineItems.5217.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_SubsequentEventTable.5216.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_SubsequentEventTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_SubsequentEventLineItems.5217.9.6" xlink:to="loc_SubsequentEventTable.5216.9.6" order="1.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:title="40903 - Disclosure - Shareholders' Equity (Warrant Exercises) (Details)" xlink:role="http://www.isoray.com/role/ShareholdersEquityWarrantExercisesDetails" xlink:type="extended">
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.6.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.6.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.6.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.8.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightAxis.1019.8.6" xlink:to="loc_ClassOfWarrantOrRightDomain.1020.8.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:type="locator" />
    <link:loc xlink:label="loc_WarrantsIssuedInNovember2010Member.49726.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsIssuedInNovember2010Member" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_WarrantsIssuedInNovember2010Member.49726.7.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsIssuedIn2011Member.49727.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsIssuedIn2011Member" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_WarrantsIssuedIn2011Member.49727.7.6" order="2.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsIssuedIn2013Member.49728.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsIssuedIn2013Member" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_WarrantsIssuedIn2013Member.49728.7.6" order="3.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_WarrantsIssuedIn2011TwoMember.49732.7.6" xlink:href="isr-20140331.xsd#isr_WarrantsIssuedIn2011TwoMember" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightDomain.1020.7.6" xlink:to="loc_WarrantsIssuedIn2011TwoMember.49732.7.6" order="2.10000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.9.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.9.6" xlink:to="loc_ClassOfWarrantOrRightTable.1025.9.6" order="5.00000" xbrldt:closed="true" xbrldt:contextElement="segment" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightAxis.1019.5.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightTable.1025.5.6" xlink:to="loc_ClassOfWarrantOrRightAxis.1019.5.6" order="1.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:type="locator" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightExercisedInPeriodExercisePriceOfWarrantsOrRights.49723.7.6" xlink:href="isr-20140331.xsd#isr_ClassOfWarrantOrRightExercisedInPeriodExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightExercisedInPeriodExercisePriceOfWarrantsOrRights.49723.7.6" order="6.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ProceedsFromWarrantExercises.14872.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ProceedsFromWarrantExercises" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ProceedsFromWarrantExercises.14872.7.6" order="7.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" xlink:href="http://xbrl.fasb.org/us-gaap/2013/elts/us-gaap-2013-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights.7037.7.6" order="6.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_LiabilityForCommonStockIssuable.49729.7.6" xlink:href="isr-20140331.xsd#isr_LiabilityForCommonStockIssuable" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_LiabilityForCommonStockIssuable.49729.7.6" order="8.00000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
    <link:loc xlink:label="loc_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares.26087.7.6" xlink:href="isr-20140331.xsd#isr_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares" xlink:type="locator" />
    <link:definitionArc xlink:from="loc_ClassOfWarrantOrRightLineItems.1022.7.6" xlink:to="loc_IssuanceOfCommonStockInConnectionWithWarrantExercisesNetOfIssuanceCostsShares.26087.7.6" order="5.50000" priority="0" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="arc" />
  </link:definitionLink>
</link:linkbase>


