<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>3</documentType><periodOfReport>2003-07-01</periodOfReport>
    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000003982</issuerCik>
        <issuerName>ALLIS CHALMERS CORP</issuerName>
        <issuerTradingSymbol>ACLM</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001252184</rptOwnerCik>
            <rptOwnerName>KEANE TERRENCE P</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>1</isOther><otherText>See Footnote (1)</otherText></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>See note</value><footnoteId id="F1"/></securityTitle><transactionAmounts><transactionShares><value>0</value></transactionShares></transactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value><footnoteId id="F1"/></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">Terrence P. Keane is President and Chief Executive Officer of AirComp L.L.C., a majority-owned subsidiary of Allis -Chalmers Corporation.</footnote></footnotes><ownerSignature><signatureName>Terrence P. Keane</signatureName><signatureDate>2003-07-01</signatureDate></ownerSignature></ownershipDocument>

