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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-05-14</periodOfReport>

    <issuer>
        <issuerCik>0001054374</issuerCik>
        <issuerName>BROADCOM CORP</issuerName>
        <issuerTradingSymbol>BRCM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001209041</rptOwnerCik>
            <rptOwnerName>HANDEL NANCY H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>5300 CALIFORNIA AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>IRVINE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>92617</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Class A common stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2009-05-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>14300</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>60324</value>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The securities awarded on 05/14/2009 are in the form of restricted stock units that will entitle the Reporting Person to receive one share of Class A common stock per restricted stock unit upon the vesting of that unit. The restricted stock units will vest, and the underlying shares will be concurrently issued, in a series of four successive equal quarterly installments over the Reporting Person's period of service as a member of the Issuer's Board of Directors as follows: (i) the first three such quarterly vesting dates shall occur on 08/05/2009, 11/05/2009, 02/05/2010 and (ii) the final quarterly vesting date shall occur upon the Reporting Person's continuation in Board service through the earlier of 05/05/2010 or the day immediately preceding the date of the Broadcom Corporation 2010 Annual Meeting of Shareholders.</footnote>
        <footnote id="F2">The securities were awarded in an exempt transaction pursuant to SEC Rule 16b-3(d).</footnote>
        <footnote id="F3">Includes (i) 39,773 shares that are held as Class A common stock and (ii) 20,551 shares in the form of restricted stock units that will entitle the Reporting Person to receive one share of Class A common stock per restricted stock unit.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Nancy H. Handel</signatureName>
        <signatureDate>2009-05-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
