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

    <documentType>4</documentType><periodOfReport>2004-01-05</periodOfReport>
    <issuer>
        <issuerCik>0000740260</issuerCik>
        <issuerName>VENTAS INC</issuerName>
        <issuerTradingSymbol>VTR</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000939563</rptOwnerCik>
            <rptOwnerName>GEARY RONALD G</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>10140 LINN STATION ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LOUISVILLE</rptOwnerCity>
            <rptOwnerState>KY</rptOwnerState>
            <rptOwnerZipCode>40223</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeTable><derivativeTransaction><securityTitle><value>Stock Option (Right to Buy)</value></securityTitle><conversionOrExercisePrice><value>22.15</value></conversionOrExercisePrice><transactionDate><value>2004-01-05</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>5000</value><footnoteId id="F1"/></transactionShares><transactionPricePerShare><value>22.15</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-01-05</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>2014-01-05</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>5000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>40000</value><footnoteId id="F3"/><footnoteId id="F4"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">Options granted pursuant to the Ventas, Inc. 2000 Stock Option Plan for Directors.</footnote><footnote id="F2">The options are exercisable in cumulative 50% annual installments beginning on 1/5/04.</footnote><footnote id="F3">Represents the total number of unexercised stock options held by Mr. Geary as of January 5, 2004.</footnote><footnote id="F4">As of January 5, 2004, Reporting Person also owns 2,425 shares of Issuer's common stock.</footnote></footnotes><remarks/><ownerSignature><signatureName>Ronald G. Geary By: T. Richard Riney, Attorney-In-Fact</signatureName><signatureDate>2004-01-07</signatureDate></ownerSignature></ownershipDocument>

