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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-04-08</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 of Digital and CMO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-04-08</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>95762</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-04-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1102</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>65.52</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>94660</value>
                    <footnoteId id="F3"/>
                </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 8, 2015, April 8, 2016 and April 8, 2017, subject to the terms and conditions of the Plan.</footnote>
        <footnote id="F2">Disposition relating to the satisfaction of tax withholding obligations upon the vesting of restricted stock unit award granted in accordance with Rule 16b-3.</footnote>
        <footnote id="F3">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, 2014).</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark L. Dosier, attorney-in-fact</signatureName>
        <signatureDate>2014-04-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2014-04-08
0000104207
WALGREEN CO
WAG
0001438864
Chawla Sona
108 WILMOT ROAD
DEERFIELD
IL
60015
0
1
0
0
President of Digital and CMO
Walgreen Co. Common Stock
2014-04-08
4
A
0
10000
0
A
95762
D
Walgreen Co. Common Stock
2014-04-09
4
F
0
1102
65.52
D
94660
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 8, 2015, April 8, 2016 and April 8, 2017, subject to the terms and conditions of the Plan.
Disposition relating to the satisfaction of tax withholding obligations upon the vesting of restricted stock unit award granted in accordance with Rule 16b-3.
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, 2014).
/s/ Mark L. Dosier, attorney-in-fact
2014-04-10