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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-10-08</periodOfReport>

    <issuer>
        <issuerCik>0000104207</issuerCik>
        <issuerName>WALGREEN CO</issuerName>
        <issuerTradingSymbol>WAG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001457648</rptOwnerCik>
            <rptOwnerName>Pugh W. Bryan</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>WALGREEN CO.</rptOwnerStreet1>
            <rptOwnerStreet2>108 WILMOT ROAD</rptOwnerStreet2>
            <rptOwnerCity>DEERFIELD</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60015</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President, Merchandising</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-10-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4900</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>36.16</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>17923</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Disposition pursuant to terms of court-approved divorce settlement agreement. The reporting person disclaims beneficial ownership of all shares disposed for the benefit of his former spouse.</footnote>
        <footnote id="F2">Includes shares underlying restricted stock units issued in lieu of dividends (through September 12, 2012) on outstanding restricted stock units and shares acquired pursuant to employee stock purchase plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John D. Curtin, attorney-in-fact</signatureName>
        <signatureDate>2012-10-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2012-10-08
0000104207
WALGREEN CO
WAG
0001457648
Pugh W. Bryan
WALGREEN CO.
108 WILMOT ROAD
DEERFIELD
IL
60015
0
1
0
0
Vice President, Merchandising
Walgreen Co. Common Stock
2012-10-08
4
J
0
4900
36.16
D
17923
D
Disposition pursuant to terms of court-approved divorce settlement agreement. The reporting person disclaims beneficial ownership of all shares disposed for the benefit of his former spouse.
Includes shares underlying restricted stock units issued in lieu of dividends (through September 12, 2012) on outstanding restricted stock units and shares acquired pursuant to employee stock purchase plan.
/s/ John D. Curtin, attorney-in-fact
2012-10-10