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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2006-06-28</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0000724024</issuerCik>
        <issuerName>AMERICAN PHYSICIANS SERVICE GROUP INC</issuerName>
        <issuerTradingSymbol>AMPH</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001297972</rptOwnerCik>
            <rptOwnerName>Boston Avenue Capital</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>15 EAST 5TH STREET</rptOwnerStreet1>
            <rptOwnerStreet2>SUITE 3200</rptOwnerStreet2>
            <rptOwnerCity>TULSA</rptOwnerCity>
            <rptOwnerState>OK</rptOwnerState>
            <rptOwnerZipCode>74103</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-06-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>35000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>14.75</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>263661</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">205,521 shares held directly by Boston Avenue Capital and 58,140 shares held by Yorktown Avenue Capital.</footnote>
    </footnotes>

    <remarks>This is a joint filing with Boston Avenue Capital, LLC as the designated filer.  Yorktown Avenue Capital, LLC; Value Fund Advisors, LLC (VFA); and Charles Gillman join in the filing.  VFA is the manager of Boston Avenue and Yorktown Avenue.  Mr. Gillman is the manager and a member of VFA.  All parties are located at the same address as Boston Avenue Capital.  In addition to the shares noted above, the following parties own the following number of shares:

Yorktown Avenue - 58,140 held directly; 205,521 held indirectly.  Yorktown disclaims beneficial ownership of the indirect shares.
VFA - 263,661 held indirectly.  VFA disclaims beneficial ownership of these shares.
Charles Gillman - 263,661 held indirectly.  Mr. Gillman disclaims beneficial ownership of these shares.</remarks>

    <ownerSignature>
        <signatureName>Frederic Dorwart</signatureName>
        <signatureDate>2006-06-29</signatureDate>
    </ownerSignature>
</ownershipDocument>
