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

    <schemaVersion>X0206</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2013-12-28</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001049606</issuerCik>
        <issuerName>COMPX INTERNATIONAL INC</issuerName>
        <issuerTradingSymbol>CIX</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001600851</rptOwnerCik>
            <rptOwnerName>Harold C. Simmons Family Trust No. 2</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THREE LINCOLN CENTER, 5430 LBJ FREEWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75240</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001600848</rptOwnerCik>
            <rptOwnerName>Harold C. Simmons Family Trust No. 1</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THREE LINCOLN CENTER, 5430 LBJ FREEWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75240</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001302221</rptOwnerCik>
            <rptOwnerName>Simmons Annette C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THREE LINCOLN CENTER, 5430 LBJ FREEWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75240</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001599736</rptOwnerCik>
            <rptOwnerName>Simmons Lisa K</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THREE LINCOLN CENTER, 5430 LBJ FREEWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75240</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001520515</rptOwnerCik>
            <rptOwnerName>CONNELLY SERENA S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>THREE LINCOLN CENTER, 5430 LBJ FREEWAY</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 1700</rptOwnerStreet2>
            <rptOwnerCity>DALLAS</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>75240</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock, par value $0.125 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>755104</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By NL</value>
                    <footnoteId id="F1"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock, par value $0.125 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5900</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Contran</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock, par value $0.125 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Kronos</value>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock, par value $0.125 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>421639</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F4"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Class A Common Stock, par value $0.125 per share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F5"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Directly held by NL Industries, Inc.  See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship of additional persons who may be deemed to beneficially own these shares.</footnote>
        <footnote id="F2">Directly held by Contran Corporation. See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship of additional persons who may be deemed to beneficially own these shares.</footnote>
        <footnote id="F3">Directly held by Kronos Worldwide, Inc..  See the Additional Information filed as Exhibit 99 to this statement for a description of the relationship of additional persons who may be deemed to beneficially own these shares.</footnote>
        <footnote id="F4">Consists of 361,217 Class A common stock shares held directly by the estate of Harold C.Simmons of which Annette C. Simmons is the independent  executor and the designated legatee of these shares and 60,422 shares she holds directly.  See the Additional Information filed as Exhibit 99 to the statement for a description of the relationships among the reporting owners..</footnote>
        <footnote id="F5">Directly held by Serena Simmons Connelly.</footnote>
    </footnotes>

    <remarks>Exhibit Index
Exhibit 99 Additional Information
Exhibit 24.1 Lisa K. Simmons Power of Attorney
Exhibit 24.2 Serena S. Connelly Power of Attorney
Exhibit 24.3 Harold C. Simmons Family Trust No. 1 Power of Attorney
Exhibit 24.4 Harold C. Simmons Family Trust No. 2 Power of Attorney
Exhibit 24.5 Annette C. Simmons Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>A. Andrew R. Louis, Attorney-in-fact, for Lisa K. Simmons, Co-Trustee of the Harold C. Simmons Family Trust No. 1</signatureName>
        <signatureDate>2014-02-25</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>A. Andrew R. Louis, Attorney-in-fact, for Serena S. Connelly, Co-Trustee of the Harold C. Simmons Family Trust No. 1</signatureName>
        <signatureDate>2014-02-25</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>A. Andrew R. Louis, Attorney-in-fact, for Lisa K. Simmons, Co-Trustee of the Harold C. Simmons Family Trust No. 2</signatureName>
        <signatureDate>2014-02-25</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>A. Andrew R. Louis, Attorney-in-fact, for Serena S.Connelly, Co-Trustee of the Harold C. Simmons Family Trust No. 2</signatureName>
        <signatureDate>2014-02-25</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>A. Andrew R. Louis, Attorney-in-fact, for Annette C.Simmons</signatureName>
        <signatureDate>2014-02-25</signatureDate>
    </ownerSignature>
</ownershipDocument>
