<SUBMISSION>
<ACCESSION-NUMBER>0001179110-06-009666
<TYPE>3
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20060501
<FILING-DATE>20060502
<DATE-OF-FILING-DATE-CHANGE>20060502
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>WALLGREN DONALD A
<CIK>0001361223
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>3
<ACT>34
<FILE-NUMBER>000-23211
<FILM-NUMBER>06798184
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>802-775-0325
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>25 GREENS HILL LANE
<CITY>RUTLAND
<STATE>VT
<ZIP>05701
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>CASELLA WASTE SYSTEMS INC
<CIK>0000911177
<ASSIGNED-SIC>4953
<IRS-NUMBER>030338873
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>0430
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>25 GREENS HILL LANE P O BOX 866
<CITY>RUTLAND
<STATE>VT
<ZIP>05701
<PHONE>8027750325
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>25 GREENE HILL ROAD
<CITY>RUTLAND
<STATE>VT
<ZIP>05702
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 3 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2006-05-01</periodOfReport>

    <noSecuritiesOwned>1</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000911177</issuerCik>
        <issuerName>CASELLA WASTE SYSTEMS INC</issuerName>
        <issuerTradingSymbol>CWST</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001361223</rptOwnerCik>
            <rptOwnerName>WALLGREN DONALD A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O CASELLA WASTE SYSTEMS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>25 GREENS HILL LANE</rptOwnerStreet2>
            <rptOwnerCity>RUTLAND</rptOwnerCity>
            <rptOwnerState>VT</rptOwnerState>
            <rptOwnerZipCode>05701</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Sr. VP, Engineering, Permittin</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes></footnotes>

    <ownerSignature>
        <signatureName>/s/Donald A. Wallgren</signatureName>
        <signatureDate>2006-05-02</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
