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  <xsd:element id="siga_PercentageOfNetProfitsFromSalesAfterNetProfitMilestoneResultingFromAwardDamages" name="PercentageOfNetProfitsFromSalesAfterNetProfitMilestoneResultingFromAwardDamages" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="siga_ProceedsFromAdvancePaymentsGovernmentContracts" name="ProceedsFromAdvancePaymentsGovernmentContracts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="siga_ProceedsFromIssuanceOfWarrantsAndOptions" name="ProceedsFromIssuanceOfWarrantsAndOptions" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="siga_ProcurementContractAndResearchAgreementsTextBlock" name="ProcurementContractAndResearchAgreementsTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="siga_ProcurementContractAxis" name="ProcurementContractAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="siga_ProcurementContractDomain" name="ProcurementContractDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="siga_ProcurementContractLineItems" name="ProcurementContractLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="siga_ProcurementContractTable" name="ProcurementContractTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="siga_RecentAccountingPronouncementsAbstract" name="RecentAccountingPronouncementsAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="siga_RecentAccountingPronouncementsTextBlock" name="RecentAccountingPronouncementsTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="siga_ReclassOfCommonStockWarrantLiabilityToAdditionalPaidInCapitalUponExercise" name="ReclassOfCommonStockWarrantLiabilityToAdditionalPaidInCapitalUponExercise" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="siga_ResearchAndDevelopmentRevenue" name="ResearchAndDevelopmentRevenue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="siga_ScheduleOfShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsValuationAssumptionsTableTextBlock" name="ScheduleOfShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsValuationAssumptionsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="siga_ShareBasedCompensationArrangementByShareBasedPaymentAwardExpirationPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardExpirationPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="siga_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesThatCouldBeIssued" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesThatCouldBeIssued" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
</xsd:schema>