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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-11-01</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001198854</rptOwnerCik>
            <rptOwnerName>SCHWARTZ DAVID Y</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>200 WILMOT ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></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>2008-11-01</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4713.2757</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>25.46</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4713.2757</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4713.2757</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The phantom stock converts into the cash value of the company's common stock on a one-for-one basis.</footnote>
        <footnote id="F2">Shares issued under Walgreen Co. Nonemployee Director Stock Plan.</footnote>
        <footnote id="F3">To be settled in two installments, the first of which occurs within thirty (30) days following termination of service as a director, and the second, one year after the first settlement date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Yuri Rozenfeld, attorney-in-fact</signatureName>
        <signatureDate>2008-11-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0303
4
2008-11-01
0000104207
WALGREEN CO
WAG
0001198854
SCHWARTZ DAVID Y
200 WILMOT ROAD
DEERFIELD
IL
60015
1
0
0
0
Phantom Stock Units
2008-11-01
4
A
0
4713.2757
25.46
A
Common Stock
4713.2757
4713.2757
D
The phantom stock converts into the cash value of the company's common stock on a one-for-one basis.
Shares issued under Walgreen Co. Nonemployee Director Stock Plan.
To be settled in two installments, the first of which occurs within thirty (30) days following termination of service as a director, and the second, one year after the first settlement date.
Yuri Rozenfeld, attorney-in-fact
2008-11-04