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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-01-25</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001213928</rptOwnerCik>
            <rptOwnerName>GELLERT JAY M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>21650 OXNARD ST., 22ND FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WOODLAND HILLS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91367</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>2005-01-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>60.168</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>24.93</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>14881.778</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Common Stock in the form of Units granted under the Non-Employee Director Deferred Stock Compensation Plan (&quot;Plan&quot;) in lieu of Director committee meeting fees pursuant to the Director's deferral election.  Such Units are payable solely in Common Stock and subject to the terms and conditions of the Director's deferral election and the Plan.</footnote>
        <footnote id="F2">Includes 8.745 Units acquired on January 13, 2005 under the Ventas Non-Employee Director Deferred Stock Compensation Plan as a result of dividend equivalents credited with respect to the dividend paid on January 13, 2005.</footnote>
        <footnote id="F3">Includes 185.556 shares acquired on January 13, 2005 under the Ventas, Inc. Distribution Reinvestment and Stock Purchase Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Jay M. Gellert By: T. Richard Riney, Attorney-In-Fact</signatureName>
        <signatureDate>2005-01-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
[{"type": "4", "sequence": "1", "filename": "edgar.xml", "description": "PRIMARY DOCUMENT", "secsgml_size_bytes": 3923}]
X0202
4
2005-01-25
0000740260
VENTAS INC
VTR
0001213928
GELLERT JAY M
21650 OXNARD ST., 22ND FLOOR
WOODLAND HILLS
CA
91367
1
0
0
0
Common Stock
2005-01-25
4
A
0
60.168
24.93
A
14881.778
D
Common Stock in the form of Units granted under the Non-Employee Director Deferred Stock Compensation Plan ("Plan") in lieu of Director committee meeting fees pursuant to the Director's deferral election.  Such Units are payable solely in Common Stock and subject to the terms and conditions of the Director's deferral election and the Plan.
Includes 8.745 Units acquired on January 13, 2005 under the Ventas Non-Employee Director Deferred Stock Compensation Plan as a result of dividend equivalents credited with respect to the dividend paid on January 13, 2005.
Includes 185.556 shares acquired on January 13, 2005 under the Ventas, Inc. Distribution Reinvestment and Stock Purchase Plan.
Jay M. Gellert By: T. Richard Riney, Attorney-In-Fact
2005-01-27