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

    <schemaVersion>X0304</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-08-15</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001188858</rptOwnerCik>
            <rptOwnerName>WAGNER MARK A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 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, Community Mgmt.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2011-08-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>12226</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>109716</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. Long-Term Performance Incentive Plan, as amended (together with the related award agreement, the &quot;Plan&quot;), which vest on October 22, 2016 and settle following the reporting person's termination of service, subject to acceleration 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 August 1, 2011) on outstanding Restricted Stock Units.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John D. Curtin, attorney-in-fact</signatureName>
        <signatureDate>2011-08-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0304
4
2011-08-15
0000104207
WALGREEN CO
WAG
0001188858
WAGNER MARK A
200 WILMOT ROAD
DEERFIELD
IL
60015
0
1
0
0
President, Community Mgmt.
Walgreen Co. Common Stock
2011-08-15
4
A
0
12226
0
A
109716
D
Shares underlying Restricted Stock Units granted under the Walgreen Co. Long-Term Performance Incentive Plan, as amended (together with the related award agreement, the "Plan"), which vest on October 22, 2016 and settle following the reporting person's termination of service, subject to acceleration in certain circumstances as set forth in the Plan.
Includes shares underlying Restricted Stock Units issued in lieu of dividends (through August 1, 2011) on outstanding Restricted Stock Units.
/s/ John D. Curtin, attorney-in-fact
2011-08-16