<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>3</documentType><periodOfReport>2003-08-05</periodOfReport>
    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001141982</issuerCik>
        <issuerName>COOPER INDUSTRIES LTD</issuerName>
        <issuerTradingSymbol>CBE</issuerTradingSymbol></issuer><reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001257901</rptOwnerCik>
            <rptOwnerName>RAYL BRIAN D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>COOPER INDUSTRIES, LTD.</rptOwnerStreet1>
            <rptOwnerStreet2>600 TRAVIS, SUITE 5800</rptOwnerStreet2>
            <rptOwnerCity>HOUSTON</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77002</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>Vice President, Personnel</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeHolding><securityTitle><value>Class A common shares</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>1167</value><footnoteId id="F1"/></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>401 (k) PlanTrustee</value></natureOfOwnership></ownershipNature></nonDerivativeHolding><nonDerivativeHolding><securityTitle><value>Class A common shares</value></securityTitle><postTransactionAmounts><sharesOwnedFollowingTransaction><value>470</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeHolding></nonDerivativeTable><derivativeTable><derivativeHolding><securityTitle><value>Employee Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>56.63</value></conversionOrExercisePrice><exerciseDate><value>2001-02-10</value></exerciseDate><expirationDate><value>2008-02-10</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Class A common shares</value></underlyingSecurityTitle><underlyingSecurityShares><value>2000</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Employee Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>43.47</value></conversionOrExercisePrice><exerciseDate><value>2002-02-09</value></exerciseDate><expirationDate><value>2009-02-09</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Class A common shares</value></underlyingSecurityTitle><underlyingSecurityShares><value>3100</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Employee Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>37.94</value></conversionOrExercisePrice><exerciseDate><value>2003-02-08</value></exerciseDate><expirationDate><value>2010-02-08</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Class A common shares</value></underlyingSecurityTitle><underlyingSecurityShares><value>5500</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Employee Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>46.10</value></conversionOrExercisePrice><exerciseDate><footnoteId id="F2"/></exerciseDate><expirationDate><value>2011-02-13</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Class A common shares</value></underlyingSecurityTitle><underlyingSecurityShares><value>4700</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Employee Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>35.21</value></conversionOrExercisePrice><exerciseDate><footnoteId id="F3"/></exerciseDate><expirationDate><value>2012-02-28</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Class A common shares</value></underlyingSecurityTitle><underlyingSecurityShares><value>5800</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding><derivativeHolding><securityTitle><value>Employee Stock Option (right to buy)</value></securityTitle><conversionOrExercisePrice><value>37.31</value></conversionOrExercisePrice><exerciseDate><footnoteId id="F4"/></exerciseDate><expirationDate><value>2008-02-11</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Class A common shares</value></underlyingSecurityTitle><underlyingSecurityShares><value>2900</value></underlyingSecurityShares></underlyingSecurity><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeHolding></derivativeTable><footnotes><footnote id="F1">Shares held under the Company's Savings and Stock Ownership Plan.</footnote><footnote id="F2">Exercisable to the extent of one-third on or after February 13, 2002; two-thirds on or after February 13, 2003, and in full on or after February 13, 2004.</footnote><footnote id="F3">Exercisable to the extent of one-third on or after February 29, 2003; two-thirds on or after February 29, 2004, and in full on or after February 28, 2005.</footnote><footnote id="F4">Exercisable to the extent of one-third on or after February 11, 2004; two-thirds on or after February 11, 2005, and in full on or after February 11, 2006.</footnote></footnotes><remarks/><ownerSignature><signatureName>Brian D. Rayl</signatureName><signatureDate>2003-08-12</signatureDate></ownerSignature></ownershipDocument>

