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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-11-12</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001188827</rptOwnerCik>
            <rptOwnerName>WASSON GREGORY D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>108 WILMOT ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>DEERFIELD</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60015</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-11-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>5</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>15000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>447118</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Charitable gift to the Walgreen Benefit Fund, an independent not-for-profit organization posthumously established  by Walgreen Co. founder Charles R. Walgreen Sr. in 1939, whose mission is to provide assistance to company employees and retirees experiencing financial distress due to circumstances beyond their control.</footnote>
        <footnote id="F2">Includes shares received upon reinvestment of dividends and shares underlying restricted stock units issued in lieu of dividends (through October 31, 2014) on outstanding restricted stock units.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark L. Dosier, attorney-in-fact</signatureName>
        <signatureDate>2014-11-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2014-11-12
0000104207
WALGREEN CO
WAG
0001188827
WASSON GREGORY D
108 WILMOT ROAD
DEERFIELD
IL
60015
1
1
0
0
President and CEO
Walgreen Co. Common Stock
2014-11-12
5
G
0
15000
0
D
447118
D
Charitable gift to the Walgreen Benefit Fund, an independent not-for-profit organization posthumously established  by Walgreen Co. founder Charles R. Walgreen Sr. in 1939, whose mission is to provide assistance to company employees and retirees experiencing financial distress due to circumstances beyond their control.
Includes shares received upon reinvestment of dividends and shares underlying restricted stock units issued in lieu of dividends (through October 31, 2014) on outstanding restricted stock units.
/s/ Mark L. Dosier, attorney-in-fact
2014-11-13