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  <xsd:element abstract="true" id="uthr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueDisclosuresAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAggregateIntrinsicValueDisclosuresAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_StockRepurchaseAbstract" name="StockRepurchaseAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_NoncurrentFederalTaxExpenseBenefit" name="NoncurrentFederalTaxExpenseBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="uthr_NoncurrentStateAndLocalTaxExpenseBenefit" name="NoncurrentStateAndLocalTaxExpenseBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="uthr_NoncurrentForeignTaxExpenseBenefit" name="NoncurrentForeignTaxExpenseBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="uthr_NoncurrentIncomeTaxExpenseBenefit" name="NoncurrentIncomeTaxExpenseBenefit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="uthr_CommercialProductsNumber" name="CommercialProductsNumber" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_ScheduleOfRevenueCostOfRevenueGrossProfitByProductTable" name="ScheduleOfRevenueCostOfRevenueGrossProfitByProductTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_RemodulinMember" name="RemodulinMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_TyvasoMember" name="TyvasoMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_AdcircaMember" name="AdcircaMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_RevenueCostOfRevenueGrossProfitByProductLineItems" name="RevenueCostOfRevenueGrossProfitByProductLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_LossContingencyPeriodForWhichLawsuitWouldPrecludeFDAFromApprovingANDA" name="LossContingencyPeriodForWhichLawsuitWouldPrecludeFDAFromApprovingANDA" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_AccredoHealthGroupIncMember" name="AccredoHealthGroupIncMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_ShareBasedCompensationArrangementByShareBasedPaymentAwardContractualTermMaximum" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardContractualTermMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityPeriodMaximum" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityPeriodMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_ShareholdersRightsPlanAbstract" name="ShareholdersRightsPlanAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_ClassOfWarrantOrRightPurchasePriceOfRightBeforeAmendmentAndRestatement" name="ClassOfWarrantOrRightPurchasePriceOfRightBeforeAmendmentAndRestatement" nillable="true" substitutionGroup="xbrli:item" type="us-types:perUnitItemType" xbrli:periodType="instant" />
  <xsd:element id="uthr_ClassOfWarrantOrRightPurchasePriceOfRightAfterAmendmentAndRestatement" name="ClassOfWarrantOrRightPurchasePriceOfRightAfterAmendmentAndRestatement" nillable="true" substitutionGroup="xbrli:item" type="us-types:perUnitItemType" xbrli:periodType="instant" />
  <xsd:element id="uthr_ClassOfWarrantOrRightSharesOfSeriesAJuniorParticipatingPreferredStockPerRight" name="ClassOfWarrantOrRightSharesOfSeriesAJuniorParticipatingPreferredStockPerRight" nillable="true" substitutionGroup="xbrli:item" type="xbrli:decimalItemType" xbrli:periodType="instant" />
  <xsd:element id="uthr_ClassOfWarrantOrRightConditionOnExerciseOfRightsMinimumPercentageOfCommonStockToBeAcquiredInTenderOffer" name="ClassOfWarrantOrRightConditionOnExerciseOfRightsMinimumPercentageOfCommonStockToBeAcquiredInTenderOffer" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element abstract="false" id="uthr_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss" name="HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="false" id="uthr_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" name="HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="false" id="uthr_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss" name="HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="uthr_OtherComprehensiveIncomeLossAmortizationGainLossAndNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax" name="OtherComprehensiveIncomeLossAmortizationGainLossAndNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="uthr_MaturityDatePrincipalBalanceLoansPayableToBank" name="MaturityDatePrincipalBalanceLoansPayableToBank" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="false" id="uthr_EstimatedAnnualEffectiveIncomeTaxRate" name="EstimatedAnnualEffectiveIncomeTaxRate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_HeldToMaturitySecuritiesDebtMaturitiesInThreeYearThroughFiveYearsNetCarryingAmount" name="HeldToMaturitySecuritiesDebtMaturitiesInThreeYearThroughFiveYearsNetCarryingAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="uthr_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveYearsNetCarryingAmount" name="HeldToMaturitySecuritiesDebtMaturitiesAfterFiveYearsNetCarryingAmount" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="uthr_HeldToMaturitySecuritiesDebtMaturitiesInThreeYearThroughFiveYearsFairValue" name="HeldToMaturitySecuritiesDebtMaturitiesInThreeYearThroughFiveYearsFairValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="uthr_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveYearsFairValue" name="HeldToMaturitySecuritiesDebtMaturitiesAfterFiveYearsFairValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="uthr_AccumulatedOtherComprehensiveIncomeLossRollForward" name="AccumulatedOtherComprehensiveIncomeLossRollForward" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_TemporaryEquityUnamortizedDiscountOnConvertibleDebtReclassifiedFromAdditionalPaidInCapitalToTemporaryEquity" name="TemporaryEquityUnamortizedDiscountOnConvertibleDebtReclassifiedFromAdditionalPaidInCapitalToTemporaryEquity" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="uthr_TemporaryEquityConvertibleNoteDue2016Member" name="TemporaryEquityConvertibleNoteDue2016Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_TemporaryEquityCommonStocksSubjectToRepurchaseMember" name="TemporaryEquityCommonStocksSubjectToRepurchaseMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="false" id="uthr_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" name="HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="false" id="uthr_ConcentrationRiskDistributorsNumber" name="ConcentrationRiskDistributorsNumber" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_OneMonthLIBORMember" name="OneMonthLIBORMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="false" id="uthr_LineOfCreditFacilityAdditionalCapacityIncreaseOption" name="LineOfCreditFacilityAdditionalCapacityIncreaseOption" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="false" id="uthr_TemporaryEquityTextBlock" name="TemporaryEquityTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="false" id="uthr_SecuritiesTermInExcessOfWhichEntityDoesNotInvest" name="SecuritiesTermInExcessOfWhichEntityDoesNotInvest" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="false" id="uthr_DebtInstrumentConversionObligationCommonStockClosingSalesPriceMinimumNumberOfTradingDays" name="DebtInstrumentConversionObligationCommonStockClosingSalesPriceMinimumNumberOfTradingDays" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="false" id="uthr_MaximumPeriodForInsuranceCompanyToPayForInsuredLoss" name="MaximumPeriodForInsuranceCompanyToPayForInsuredLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="false" id="uthr_ShareTrackingAwardPlansCurrentAndNoncurrent" name="ShareTrackingAwardPlansCurrentAndNoncurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="false" id="uthr_ShareTrackingAwardPlansNoncurrent" name="ShareTrackingAwardPlansNoncurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="uthr_ShareRepurchaseProgram2013Member" name="ShareRepurchaseProgram2013Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_ShareRepurchaseProgram2012Member" name="ShareRepurchaseProgram2012Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_ShareRepurchaseProgram2011Member" name="ShareRepurchaseProgram2011Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="uthr_AcceleratedShareRepurchaseProgramAmountPaidOrAdjustment" name="AcceleratedShareRepurchaseProgramAmountPaidOrAdjustment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="uthr_USBasedDistributorsMember" name="USBasedDistributorsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="false" id="uthr_CostOfRevenues" name="CostOfRevenues" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="uthr_IncreaseDecreaseInInsuranceProceedsReceivable" name="IncreaseDecreaseInInsuranceProceedsReceivable" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" />
  <xsd:element id="uthr_AvailableForSaleSecuritiesEquitySecuritiesInvestmentPercentageLessThan" name="AvailableForSaleSecuritiesEquitySecuritiesInvestmentPercentageLessThan" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" />
  <xsd:element id="uthr_PrivatelyHeldCorporationsMember" name="PrivatelyHeldCorporationsMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="uthr_FederalFundsEffectiveRateMember" name="FederalFundsEffectiveRateMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="uthr_WellsFargoPrimeRateMember" name="WellsFargoPrimeRateMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="uthr_NumberOfEligibleEmployeesWhoMayPurchaseMoreThanFourThousandSharesDuringOfferingPeriod" name="NumberOfEligibleEmployeesWhoMayPurchaseMoreThanFourThousandSharesDuringOfferingPeriod" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="uthr_SyntheticGenomicsIncMember" name="SyntheticGenomicsIncMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <element id="uthr_OrenitramMember" name="OrenitramMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
</xsd:schema>


