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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-04-09</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001438864</rptOwnerCik>
            <rptOwnerName>Chawla Sona</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>108 WILMOT ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></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>President, E-Commerce</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2013-04-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>10000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>70610</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares underlying restricted stock units granted under the Walgreen Co. 2013 Omnibus Incentive Plan (together with the related award agreement, the &quot;Plan&quot;), which vest in three equal annual installments of one-third on April 9, 2014, April 9, 2015 and April 9, 2016, subject to the terms and conditions of the Plan.</footnote>
        <footnote id="F2">Includes shares received upon reinvestment of dividends and shares underlying restricted stock units issued in lieu of dividends on outstanding restricted stock units (through March 12, 2013).</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John D. Curtin, attorney-in-fact</signatureName>
        <signatureDate>2013-04-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2013-04-09
0000104207
WALGREEN CO
WAG
0001438864
Chawla Sona
108 WILMOT ROAD
DEERFIELD
IL
60015
0
1
0
0
President, E-Commerce
Walgreen Co. Common Stock
2013-04-09
4
A
0
10000
0
A
70610
D
Shares underlying restricted stock units granted under the Walgreen Co. 2013 Omnibus Incentive Plan (together with the related award agreement, the "Plan"), which vest in three equal annual installments of one-third on April 9, 2014, April 9, 2015 and April 9, 2016, subject to the terms and conditions of the Plan.
Includes shares received upon reinvestment of dividends and shares underlying restricted stock units issued in lieu of dividends on outstanding restricted stock units (through March 12, 2013).
/s/ John D. Curtin, attorney-in-fact
2013-04-11