<XBRL>
<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with WebFilings-->
<!-- -->
<xsd:schema attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.regeneron.com/20120930" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:nonnum="http://www.xbrl.org/dtr/type/non-numeric" xmlns:num="http://www.xbrl.org/dtr/type/numeric" xmlns:regn="http://www.regeneron.com/20120930" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:import namespace="http://fasb.org/us-gaap/2011-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2011/elts/us-gaap-2011-01-31.xsd" />
  <xsd:import namespace="http://fasb.org/us-roles/2011-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2011/elts/us-roles-2011-01-31.xsd" />
  <xsd:import namespace="http://fasb.org/us-types/2011-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2011/elts/us-types-2011-01-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/arcrole/fact-explanatoryFact" schemaLocation="http://www.xbrl.org/lrr/arcrole/factExplanatory-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/net" schemaLocation="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/non-numeric" schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/numeric" schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/country/2011-01-31" schemaLocation="http://xbrl.sec.gov/country/2011/country-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/currency/2011-01-31" schemaLocation="http://xbrl.sec.gov/currency/2011/currency-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2011-01-31" schemaLocation="http://xbrl.sec.gov/dei/2011/dei-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/exch/2011-01-31" schemaLocation="http://xbrl.sec.gov/exch/2011/exch-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/invest/2011-01-31" schemaLocation="http://xbrl.sec.gov/invest/2011/invest-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/naics/2011-01-31" schemaLocation="http://xbrl.sec.gov/naics/2011/naics-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/sic/2011-01-31" schemaLocation="http://xbrl.sec.gov/sic/2011/sic-2011-01-31.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/stpr/2011-01-31" schemaLocation="http://xbrl.sec.gov/stpr/2011/stpr-2011-01-31.xsd" />
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="regn-20120930_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="regn-20120930_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="regn-20120930_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple" />
      <link:linkbaseRef xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="regn-20120930_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple" />
      <link:roleType id="AccountsPayableAndAccruedExpenses" roleURI="http://www.regeneron.com/role/AccountsPayableAndAccruedExpenses">
        <link:definition>2108100 - Disclosure - Accounts Payable and Accrued Expenses</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AccountsPayableAndAccruedExpensesDetails" roleURI="http://www.regeneron.com/role/AccountsPayableAndAccruedExpensesDetails">
        <link:definition>2408402 - Disclosure - Accounts Payable and Accrued Expenses (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AccountsPayableAndAccruedExpensesTables" roleURI="http://www.regeneron.com/role/AccountsPayableAndAccruedExpensesTables">
        <link:definition>2308301 - Disclosure - Accounts Payable and Accrued Expenses (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedBalanceSheetsUnaudited" roleURI="http://www.regeneron.com/role/CondensedBalanceSheetsUnaudited">
        <link:definition>1001000 - Statement - CONDENSED BALANCE SHEETS (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedBalanceSheetsUnauditedParenthetical" roleURI="http://www.regeneron.com/role/CondensedBalanceSheetsUnauditedParenthetical">
        <link:definition>1001501 - Statement - CONDENSED BALANCE SHEETS (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedStatementsOfCashFlowsUnaudited" roleURI="http://www.regeneron.com/role/CondensedStatementsOfCashFlowsUnaudited">
        <link:definition>1004000 - Statement - CONDENSED STATEMENTS OF CASH FLOWS (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedStatementsOfOperationsAndComprehensiveIncomeLossUnaudited" roleURI="http://www.regeneron.com/role/CondensedStatementsOfOperationsAndComprehensiveIncomeLossUnaudited">
        <link:definition>1002000 - Statement - CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedStatementsOfStockholdersEquityUnaudited" roleURI="http://www.regeneron.com/role/CondensedStatementsOfStockholdersEquityUnaudited">
        <link:definition>1003000 - Statement - CONDENSED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DocumentAndEntityInformation" roleURI="http://www.regeneron.com/role/DocumentAndEntityInformation">
        <link:definition>0001000 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurements" roleURI="http://www.regeneron.com/role/FairValueMeasurements">
        <link:definition>2106100 - Disclosure - Fair Value Measurements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsDetails" roleURI="http://www.regeneron.com/role/FairValueMeasurementsDetails">
        <link:definition>2406402 - Disclosure - Fair Value Measurements (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueMeasurementsTables" roleURI="http://www.regeneron.com/role/FairValueMeasurementsTables">
        <link:definition>2306301 - Disclosure - Fair Value Measurements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxes" roleURI="http://www.regeneron.com/role/IncomeTaxes">
        <link:definition>2109100 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesDetails" roleURI="http://www.regeneron.com/role/IncomeTaxesDetails">
        <link:definition>2409401 - Disclosure - Income Taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InterimFinancialStatements" roleURI="http://www.regeneron.com/role/InterimFinancialStatements">
        <link:definition>2101100 - Disclosure - Interim Financial Statements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Inventory" roleURI="http://www.regeneron.com/role/Inventory">
        <link:definition>2107100 - Disclosure - Inventory</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InventoryDetails" roleURI="http://www.regeneron.com/role/InventoryDetails">
        <link:definition>2407402 - Disclosure - Inventory (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="InventoryTables" roleURI="http://www.regeneron.com/role/InventoryTables">
        <link:definition>2307301 - Disclosure - Inventory (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LegalMatters" roleURI="http://www.regeneron.com/role/LegalMatters">
        <link:definition>2110100 - Disclosure - Legal Matters</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LegalMattersDetails" roleURI="http://www.regeneron.com/role/LegalMattersDetails">
        <link:definition>2410402 - Disclosure - Legal Matters (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LegalMattersPolicies" roleURI="http://www.regeneron.com/role/LegalMattersPolicies">
        <link:definition>2210201 - Disclosure - Legal Matters (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecurities" roleURI="http://www.regeneron.com/role/MarketableSecurities">
        <link:definition>2105100 - Disclosure - Marketable Securities</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesDetails" roleURI="http://www.regeneron.com/role/MarketableSecuritiesDetails">
        <link:definition>2405402 - Disclosure - Marketable Securities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="MarketableSecuritiesTables" roleURI="http://www.regeneron.com/role/MarketableSecuritiesTables">
        <link:definition>2305301 - Disclosure - Marketable Securities (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PerShareData" roleURI="http://www.regeneron.com/role/PerShareData">
        <link:definition>2103100 - Disclosure - Per Share Data</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PerShareDataDetails" roleURI="http://www.regeneron.com/role/PerShareDataDetails">
        <link:definition>2403402 - Disclosure - Per Share Data (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="PerShareDataTables" roleURI="http://www.regeneron.com/role/PerShareDataTables">
        <link:definition>2303301 - Disclosure - Per Share Data (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RecentlyIssuedAccountingStandards" roleURI="http://www.regeneron.com/role/RecentlyIssuedAccountingStandards">
        <link:definition>2111100 - Disclosure - Recently Issued Accounting Standards</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Revenue" roleURI="http://www.regeneron.com/role/Revenue">
        <link:definition>2102100 - Disclosure - Revenue</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueDetails" roleURI="http://www.regeneron.com/role/RevenueDetails">
        <link:definition>2402403 - Disclosure - Revenue (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenuePolicies" roleURI="http://www.regeneron.com/role/RevenuePolicies">
        <link:definition>2202201 - Disclosure - Revenue (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueTables" roleURI="http://www.regeneron.com/role/RevenueTables">
        <link:definition>2302302 - Disclosure - Revenue (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StatementOfCashFlows" roleURI="http://www.regeneron.com/role/StatementOfCashFlows">
        <link:definition>2104100 - Disclosure - Statement of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StatementOfCashFlowsDetails" roleURI="http://www.regeneron.com/role/StatementOfCashFlowsDetails">
        <link:definition>2404401 - Disclosure - Statement of Cash Flows (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element id="regn_AccruedCapitalExpenditures" name="AccruedCapitalExpenditures" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="regn_AccruedClinicalTrialExpenseCurrent" name="AccruedClinicalTrialExpenseCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="regn_AccruedSalesRelatedDeductionsAndRoyalties" name="AccruedSalesRelatedDeductionsAndRoyalties" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="regn_AmountOfPaymentMadeUponReachingMinimumSalesTarget" name="AmountOfPaymentMadeUponReachingMinimumSalesTarget" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="regn_ArcalystNetProductSalesMember" name="ArcalystNetProductSalesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsGrossUnrealizedGains" name="AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsGrossUnrealizedGains" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="regn_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsGrossUnrealizedLoss" name="AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsGrossUnrealizedLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="regn_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsGrossUnrealizedGains" name="AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsGrossUnrealizedGains" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="regn_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsGrossUnrealizedLoss" name="AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsGrossUnrealizedLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="regn_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearGrossUnrealizedGains" name="AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearGrossUnrealizedGains" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="regn_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearGrossUnrealizedLoss" name="AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearGrossUnrealizedLoss" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="regn_ClassificationOfInvestmentAxis" name="ClassificationOfInvestmentAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_ClassificationOfInvestmentDomain" name="ClassificationOfInvestmentDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_CollaborationAgreementWithBayerHealthcareLlcMember" name="CollaborationAgreementWithBayerHealthcareLlcMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_CollaborationAgreementWithSanofiMember" name="CollaborationAgreementWithSanofiMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_CumulativeSalesRangeMaximum" name="CumulativeSalesRangeMaximum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="regn_CumulativeSalesRangeMinimum" name="CumulativeSalesRangeMinimum" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="regn_DeferredRevenueFromRelatedPartyCurrent" name="DeferredRevenueFromRelatedPartyCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="regn_DeferredRevenueFromRelatedPartyNoncurrent" name="DeferredRevenueFromRelatedPartyNoncurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="regn_DistributionRelatedFeesMember" name="DistributionRelatedFeesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_EntityWideRevenueMajorCustomerPercentage" name="EntityWideRevenueMajorCustomerPercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_EquitySecurityFairValueDisclosure" name="EquitySecurityFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="regn_EuropeMember" name="EuropeMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_EyleaNetProductSalesMember" name="EyleaNetProductSalesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_FacilityLeaseObligationsCurrent" name="FacilityLeaseObligationsCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="regn_FacilityLeaseObligationsNoncurrent" name="FacilityLeaseObligationsNoncurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="regn_GrosssalesrevenueMember" name="GrosssalesrevenueMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_IncomeLossFromProductsCommercializedByOurCollaborationPartner" name="IncomeLossFromProductsCommercializedByOurCollaborationPartner" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="regn_IncrementalCommonSharesAttributableToNonvestedRestrictedShares" name="IncrementalCommonSharesAttributableToNonvestedRestrictedShares" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_InterimFinancialStatementsAbstract" name="InterimFinancialStatementsAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_LicenseAgreementWithGenentechMember" name="LicenseAgreementWithGenentechMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_LossContingenciesByGeographicAreaAxis" name="LossContingenciesByGeographicAreaAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_LossContingenciesByGeographicAreaDomain" name="LossContingenciesByGeographicAreaDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_MortgageBackedSecuritiesFairValueDisclosure" name="MortgageBackedSecuritiesFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="regn_MunicipalBondsFairValueDisclosure" name="MunicipalBondsFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="regn_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" name="NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_NumberOfMarketableSecuritiesHeld" name="NumberOfMarketableSecuritiesHeld" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="regn_OtherCollaborationRevenue" name="OtherCollaborationRevenue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_OtherSalesRelatedDeductionsMember" name="OtherSalesRelatedDeductionsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_RebatesAndChargebacksMember" name="RebatesAndChargebacksMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_RestrictedMember" name="RestrictedMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_RevenueAndConcentrationRiskDisclosureTextBlock" name="RevenueAndConcentrationRiskDisclosureTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_RevenueDisclosureLineItems" name="RevenueDisclosureLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_RevenueDisclosureTable" name="RevenueDisclosureTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_RoyaltyPaymentPercentageOfCumulativeSalesOverRange" name="RoyaltyPaymentPercentageOfCumulativeSalesOverRange" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_RoyaltyPaymentPercentageOfCumulativeSalesWithinRange" name="RoyaltyPaymentPercentageOfCumulativeSalesWithinRange" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_ScheduleOfSalesRelatedDeductionsActivityTableTextBlock" name="ScheduleOfSalesRelatedDeductionsActivityTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_USGovernmentGuaranteedCollateralizedMortgageObligationsFairValueDisclosure" name="USGovernmentGuaranteedCollateralizedMortgageObligationsFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="regn_USGovernmentGuaranteedCorporateBondsFairValueDisclosure" name="USGovernmentGuaranteedCorporateBondsFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="regn_USGovernmentGuaranteedCorporateBondsMember" name="USGovernmentGuaranteedCorporateBondsMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="regn_USGovernmentObligationsFairValueDisclosure" name="USGovernmentObligationsFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="regn_UnrestrictedMember" name="UnrestrictedMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="regn_ZaltrapMember" name="ZaltrapMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
</xsd:schema>
</XBRL>
