<SUBMISSION>
<ACCESSION-NUMBER>0001022079-06-000068
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20060522
<FILING-DATE>20060524
<DATE-OF-FILING-DATE-CHANGE>20060524
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>QUEST DIAGNOSTICS INC
<CIK>0001022079
<ASSIGNED-SIC>8071
<IRS-NUMBER>161387862
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>ONE MALCOLM AVE
<CITY>TETERBORO
<STATE>NJ
<ZIP>07608
<PHONE>2013935000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>ONE MALCOLM AVE
<CITY>TETERBORO
<STATE>NJ
<ZIP>07601
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>CORNING CLINICAL LABORATORIES INC
<DATE-CHANGED>19960903
</FORMER-COMPANY>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>MOHAPATRA SURYA N
<CIK>0001222671
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-12215
<FILM-NUMBER>06864576
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>QUEST DIAGNOSTICS INC
<STREET2>ONE MALCOLM AVE
<CITY>TETERBORO
<STATE>NJ
<ZIP>07608
</BUSINESS-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
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        <issuerTradingSymbol>DGX</issuerTradingSymbol>
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            <rptOwnerStreet2>1290 WALL STREET WEST</rptOwnerStreet2>
            <rptOwnerCity>LYNDHURST</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07071</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
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                <value></value>
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    </derivativeTable>

    <footnotes>
        <footnote id="F1">On June 20, 2005, the Company effected a 2-for-1 stock split of the Common Stock in the form of a 100% stock dividend.  All prior holdings, including stock options, have been adjusted to reflect the stock split.  This amount also includes 29,542 shares directly beneficially owned by Reporting Person as grantor/trustee of a qualified Grantor Retained Annuity Trust.

Reporting Person is in compliance with the Company's executive share ownership guidelines.</footnote>
        <footnote id="F2">These underlying shares were acquired on a periodic basis by the trustee of the Company's tax qualified Profit Sharing (401(k)) and Supplemental Deferred Compensation Plans.  The information was obtained from the plan administrator as of a recent date.  The number of shares is based on the account balance of the Company stock fund under the plans (which include some money market instruments) divided by the market price of the Company's stock as of that date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Michael E. Prevoznik, atty-in-fact for Surya N. Mohapatra</signatureName>
        <signatureDate>2006-05-24</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
