<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-05-21</periodOfReport>

    <issuer>
        <issuerCik>0000740260</issuerCik>
        <issuerName>VENTAS INC</issuerName>
        <issuerTradingSymbol>VTR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001042563</rptOwnerCik>
            <rptOwnerName>THEOBALD THOMAS C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>227 WEST MONROE, STE. 3500</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>CHICAGO</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60606</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2004-05-21</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1750</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8750</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F3"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">These shares represent restricted shares granted under the 2004 Stock Plan for Directors.  These shares vest in annual installments of 1/2 on first anniversary of grant and 1/2 on second anniversary of grant (May 21, 2005 and May 21, 2006, respectively).</footnote>
        <footnote id="F2">As of May 21, 2004, Reporting Person also owns options to purchase 25,000 shares of Issuer's common stock.</footnote>
        <footnote id="F3">Reporting Person as of May 21, 2004, owns 2,000 of the 8,750 Total Beneficially Owned, Indirectly through Trust for Son</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Thomas C. Theobald, By: T. Richard Riney, Attorney-In-Fact</signatureName>
        <signatureDate>2004-05-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0202
4
2004-05-21
0000740260
VENTAS INC
VTR
0001042563
THEOBALD THOMAS C
227 WEST MONROE, STE. 3500
CHICAGO
IL
60606
1
0
0
0
Common Stock
2004-05-21
4
A
0
1750
0
A
8750
D
These shares represent restricted shares granted under the 2004 Stock Plan for Directors.  These shares vest in annual installments of 1/2 on first anniversary of grant and 1/2 on second anniversary of grant (May 21, 2005 and May 21, 2006, respectively).
As of May 21, 2004, Reporting Person also owns options to purchase 25,000 shares of Issuer's common stock.
Reporting Person as of May 21, 2004, owns 2,000 of the 8,750 Total Beneficially Owned, Indirectly through Trust for Son
Thomas C. Theobald, By: T. Richard Riney, Attorney-In-Fact
2004-05-25