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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

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

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001377143</rptOwnerCik>
            <rptOwnerName>Atkinson Graham W</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>Senior Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-10-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7872</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30092</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On October 10, 2012, the Compensation Committee determined that the the performance criteria applicable to this restricted stock unit award granted on September 1, 2011 under the Walgreen Co. Long-Term Performance Incentive Plan (together with the related award agreement, the &quot;Plan&quot;) and initially reported in a Form 4 filed on September 2, 2011, had been satisfied.  The shares underlying these restricted stock units will vest on September 1, 2014, subject to acceleration or forefeiture in certain circumstances as set forth in the Plan.</footnote>
        <footnote id="F2">Includes shares underlying Restricted Stock Units issued in lieu of dividends (through September 12, 2012) on outstanding Restricted Stock Units, including 225 shares with respect to the restricted stock unit award described in note (1) above.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark L. Dosier, Attorney-in-Fact</signatureName>
        <signatureDate>2012-10-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2012-10-10
0000104207
WALGREEN CO
WAG
0001377143
Atkinson Graham W
WALGREEN CO.
108 WILMOT ROAD
DEERFIELD
IL
60015
0
1
0
0
Senior Vice President
Walgreen Co. Common Stock
2012-10-10
4
A
0
7872
0
A
30092
D
On October 10, 2012, the Compensation Committee determined that the the performance criteria applicable to this restricted stock unit award granted on September 1, 2011 under the Walgreen Co. Long-Term Performance Incentive Plan (together with the related award agreement, the "Plan") and initially reported in a Form 4 filed on September 2, 2011, had been satisfied.  The shares underlying these restricted stock units will vest on September 1, 2014, subject to acceleration or forefeiture in certain circumstances as set forth in the Plan.
Includes shares underlying Restricted Stock Units issued in lieu of dividends (through September 12, 2012) on outstanding Restricted Stock Units, including 225 shares with respect to the restricted stock unit award described in note (1) above.
/s/ Mark L. Dosier, Attorney-in-Fact
2012-10-12