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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2004-10-01</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000065100</issuerCik>
        <issuerName>MERRILL LYNCH &amp; CO INC</issuerName>
        <issuerTradingSymbol>MER</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001237642</rptOwnerCik>
            <rptOwnerName>ROSSOTTI CHARLES O</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MERRILL LYNCH &amp; CO., INC.</rptOwnerStreet1>
            <rptOwnerStreet2>4 WORLD FINANCIAL CENTER</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10080</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <remarks>Exhibit List: Exhibit 24 - Power of Attorney</remarks>

    <ownerSignature>
        <signatureName>Charles O. Rossotti                        (by Michael A. LaMaina, as agent)</signatureName>
        <signatureDate>2004-10-05</signatureDate>
    </ownerSignature>
</ownershipDocument>

