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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2014-10-07</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001276108</rptOwnerCik>
            <rptOwnerName>SCHOLZ MIA M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>108 WILMONT 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>SVP - Corp. Fin. Operations</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2014-10-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4146</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>47084</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>2014-10-07</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>7500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>54584</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On October 7, 2014, the Compensation Committee determined that the performance criteria applicable to this restricted stock unit award granted on November 1, 2013 (not a derivative security within the meaning of Rule 16a-1(c) upon grant) under the Walgreen Co. 2013 Omnibus Incentive Plan (together with the related award agreement, the &quot;Plan&quot;) had been satisfied. The shares underlying these restricted stock units will vest on November 1, 2016, subject to the terms and conditions of the Plan.</footnote>
        <footnote id="F2">On October 7, 2014, the Compensation Committee determined that the performance criteria applicable to this restricted stock unit award granted on December 10, 2013 (not a derivative security within the meaning of Rule 16a-1(c) upon grant) under the Plan had been satisfied. The shares underlying these restricted stock units will vest on August 31, 2015, subject to the terms and conditions of the Plan.</footnote>
        <footnote id="F3">Includes shares received upon reinvestment of dividends and shares underlying restricted stock units issued in lieu of dividends (through September 12, 2014) on outstanding restricted stock units, including 84 shares with respect to the restricted stock unit award described in note (1) above and 113 shares with respect to the retricted stock unit award described in note (2) above.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark L. Dosier, attorney-in-fact</signatureName>
        <signatureDate>2014-10-08</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2014-10-07
0000104207
WALGREEN CO
WAG
0001276108
SCHOLZ MIA M
108 WILMONT ROAD
DEERFIELD
IL
60015
0
1
0
0
SVP - Corp. Fin. Operations
Walgreen Co. Common Stock
2014-10-07
4
A
0
4146
0
A
47084
D
Walgreen Co. Common Stock
2014-10-07
4
A
0
7500
0
A
54584
D
On October 7, 2014, the Compensation Committee determined that the performance criteria applicable to this restricted stock unit award granted on November 1, 2013 (not a derivative security within the meaning of Rule 16a-1(c) upon grant) under the Walgreen Co. 2013 Omnibus Incentive Plan (together with the related award agreement, the "Plan") had been satisfied. The shares underlying these restricted stock units will vest on November 1, 2016, subject to the terms and conditions of the Plan.
On October 7, 2014, the Compensation Committee determined that the performance criteria applicable to this restricted stock unit award granted on December 10, 2013 (not a derivative security within the meaning of Rule 16a-1(c) upon grant) under the Plan had been satisfied. The shares underlying these restricted stock units will vest on August 31, 2015, 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 (through September 12, 2014) on outstanding restricted stock units, including 84 shares with respect to the restricted stock unit award described in note (1) above and 113 shares with respect to the retricted stock unit award described in note (2) above.
/s/ Mark L. Dosier, attorney-in-fact
2014-10-08