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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-10-10</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>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, Community Mgmt.</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Walgreen Co. Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-10-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>13454</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>127655</value>
                    <footnoteId id="F4"/>
                </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>2012-10-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>23402</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>151057</value>
                    <footnoteId id="F4"/>
                </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>2012-10-10</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>9105</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>35.63</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>141952</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">On October 10, 2012, the Compensation Committee determined that the the performance criteria applicable to this restricted stock unit award granted on September 1, 2011 under the Walgreen Co. Long-Term Performance Incentive Plan (together with the related award agreement, the &quot;Plan&quot;) and initially reported in a Form 4 filed on September 2, 2011, had been satisfied.  The shares underlying these restricted stock units will vest on September 1, 2014, subject to acceleration or forefeiture in certain circumstances as set forth in the Plan.</footnote>
        <footnote id="F2">Shares issued upon settlement of peformance share award (not a derivative security within the meaning of Rule 16a-1(c)) granted on September 1, 2009 under the Plan.</footnote>
        <footnote id="F3">Disposition relating to the satisfaction of tax withholding obligations upon the settlement of performance share award granted in accordance with Rule 16b-3.</footnote>
        <footnote id="F4">Includes shares underlying restricted stock units issued in lieu of dividends (through September 12, 2012) on outstanding restricted stock units, including 384 shares with respect to the restricted stock unit award described in note (1) above.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John D. Curtin, attorney-in-fact</signatureName>
        <signatureDate>2012-10-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
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X0306
4
2012-10-10
0000104207
WALGREEN CO
WAG
0001188858
WAGNER MARK A
108 WILMOT ROAD
DEERFIELD
IL
60015
0
1
0
0
President, Community Mgmt.
Walgreen Co. Common Stock
2012-10-10
4
A
0
13454
0
A
127655
D
Walgreen Co. Common Stock
2012-10-10
4
A
0
23402
0
A
151057
D
Walgreen Co. Common Stock
2012-10-10
4
F
0
9105
35.63
D
141952
D
On October 10, 2012, the Compensation Committee determined that the the performance criteria applicable to this restricted stock unit award granted on September 1, 2011 under the Walgreen Co. Long-Term Performance Incentive Plan (together with the related award agreement, the "Plan") and initially reported in a Form 4 filed on September 2, 2011, had been satisfied.  The shares underlying these restricted stock units will vest on September 1, 2014, subject to acceleration or forefeiture in certain circumstances as set forth in the Plan.
Shares issued upon settlement of peformance share award (not a derivative security within the meaning of Rule 16a-1(c)) granted on September 1, 2009 under the Plan.
Disposition relating to the satisfaction of tax withholding obligations upon the settlement of performance share award granted in accordance with Rule 16b-3.
Includes shares underlying restricted stock units issued in lieu of dividends (through September 12, 2012) on outstanding restricted stock units, including 384 shares with respect to the restricted stock unit award described in note (1) above.
/s/ John D. Curtin, attorney-in-fact
2012-10-12