<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

<documentType>4/A</documentType><periodOfReport>2003-05-02</periodOfReport><dateOfOriginalSubmission>2003-05-05</dateOfOriginalSubmission>
<issuer><issuerCik>0000740260</issuerCik>
        <issuerName>VENTAS INC</issuerName>
<issuerTradingSymbol>VTR</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001215185</rptOwnerCik>
            <rptOwnerName>RINEY T RICHARD</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
<reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Executive Vice President</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-05-02</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>12500</value></transactionShares><transactionValue><value>4.69</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>280247</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-05-02</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved><footnoteId id="F1"/></transactionCoding><transactionAmounts><transactionShares><value>12500</value></transactionShares><transactionValue><value>13.0027</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>267747</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity><derivativeSecurity><securityTitle><value>Stock Option (Right to Buy)</value></securityTitle><conversionOrExercisePrice><value>4.69</value></conversionOrExercisePrice><transactionDate><value>2003-05-02</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>12500</value></transactionShares><transactionValue><value>4.69</value></transactionValue><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2000-05-13</value><footnoteId id="F3"/></exerciseDate><expirationDate><value>2009-05-13</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>12500</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>372646</value><footnoteId id="F4"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">On May 2, 2003, the Reporting Person transmitted to the Securities and Exchange Commission a Form 144 covering the sale of the Issuer's common stock reported on Table I.</footnote><footnote id="F2">Reporting Person also owns 1,300 shares indirectly by IRA.</footnote><footnote id="F3">These options were part of a previously reported grant of 50,000 shares on May 13, 1999 by the Issuer to Reporting Person that vested in three equal installments on May 13, 2000, May 13, 2001 and May 13, 2002.</footnote><footnote id="F4">Represents total number of unexercised stock options held by Mr. Riney as of May 2, 2003.</footnote></footnotes><ownerSignature><signatureName>T. Richard Riney</signatureName><signatureDate>2003-05-07</signatureDate></ownerSignature></ownershipDocument>

