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

    <schemaVersion>X0304</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2011-11-01</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001179715</rptOwnerCik>
            <rptOwnerName>SKINNER JAMES A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>WALGREEN CO.</rptOwnerStreet1>
            <rptOwnerStreet2>108 WILMOT ROAD</rptOwnerStreet2>
            <rptOwnerCity>DEERFIELD</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60015</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2011-11-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4788.384</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>32.37</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4788.384</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>38509.3</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The phantom stock is issued under the Walgreen Co. Nonemployee Director Stock Plan and converts into the cash value of the company's common stock on a one-for-one basis.</footnote>
        <footnote id="F2">To be settled in two installments, the first of which occurs within thirty days following termination of service as a director, and the second, one year after the first settlement date.</footnote>
        <footnote id="F3">Includes phantom stock units issued in lieu of dividends (through September 12, 2011) on outstanding phantom stock units and 37.707 units that inadvertently were omitted from the Statement of Changes in Beneficial Ownership of Securities filed on October 14, 2011.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mark L. Dosier, Attorney-in-Fact</signatureName>
        <signatureDate>2011-11-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0304
4
2011-11-01
0000104207
WALGREEN CO
WAG
0001179715
SKINNER JAMES A
WALGREEN CO.
108 WILMOT ROAD
DEERFIELD
IL
60015
1
0
0
0
Phantom Stock Units
2011-11-01
4
A
0
4788.384
32.37
A
Common Stock
4788.384
38509.3
D
The phantom stock is issued under the Walgreen Co. Nonemployee Director Stock Plan and converts into the cash value of the company's common stock on a one-for-one basis.
To be settled in two installments, the first of which occurs within thirty days following termination of service as a director, and the second, one year after the first settlement date.
Includes phantom stock units issued in lieu of dividends (through September 12, 2011) on outstanding phantom stock units and 37.707 units that inadvertently were omitted from the Statement of Changes in Beneficial Ownership of Securities filed on October 14, 2011.
/s/ Mark L. Dosier, Attorney-in-Fact
2011-11-02