<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-12-29</periodOfReport>
    <issuer>
        <issuerCik>0000740260</issuerCik>
        <issuerName>VENTAS INC</issuerName>
        <issuerTradingSymbol>VTR</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001215188</rptOwnerCik>
            <rptOwnerName>CAFARO DEBRA A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10350 ORMSBY PARK PLACE, SUITE 300</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOUISVILLE,</rptOwnerCity>
            <rptOwnerState>KY</rptOwnerState>
            <rptOwnerZipCode>40223</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Chairman, President and CEO</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-12-29</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>36639</value></transactionShares><transactionPricePerShare><value>8.1875</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>756476</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeTransaction></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Stock Option (Right to Buy)</value></securityTitle><conversionOrExercisePrice><value>8.1875</value></conversionOrExercisePrice><transactionDate><value>2003-12-29</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>36639</value></transactionShares><transactionPricePerShare><value>8.1875</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1999-03-05</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>2009-03-05</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>36639</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>681619</value><footnoteId id="F2"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">These options were part of a previously reported grant of 36,639 shares on March 5, 1999 by the Issuer to the Reporting Person that vested in three equal installments on March 5, 1999, March 5, 2000 and March 5, 2001.</footnote><footnote id="F2">Represents total number of unexercised stock options held by Ms. Cafaro as of December 29, 2003.</footnote></footnotes><remarks/><ownerSignature><signatureName>Debra A. Cafaro</signatureName><signatureDate>2003-12-30</signatureDate></ownerSignature></ownershipDocument>
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X0201
4
2003-12-29
0000740260
VENTAS INC
VTR
0001215188
CAFARO DEBRA A
10350 ORMSBY PARK PLACE, SUITE 300
LOUISVILLE,
KY
40223
1
1
0
0
Chairman, President and CEO
Common Stock
2003-12-29
4
M
0
36639
8.1875
A
756476
D
Stock Option (Right to Buy)
8.1875
2003-12-29
4
M
0
36639
8.1875
D
1999-03-05
2009-03-05
Common Stock
36639
681619
D
These options were part of a previously reported grant of 36,639 shares on March 5, 1999 by the Issuer to the Reporting Person that vested in three equal installments on March 5, 1999, March 5, 2000 and March 5, 2001.
Represents total number of unexercised stock options held by Ms. Cafaro as of December 29, 2003.
Debra A. Cafaro
2003-12-30