-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
Originator-Key-Asymmetric:
 MFgwCgYEVQgBAQICAf8DSgAwRwJAW2sNKK9AVtBzYZmr6aGjlWyK3XmZv3dTINen
 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 OgN+S9noRo8KrefeoF4FRNAKMA74y9wXFMT8czttdlVh+BbRX3v1qyv9KmFTUFtu
 /hqBOuB71zvkVz+CK0khQA==

<SEC-DOCUMENT>0001179110-04-016861.txt : 20040820
<SEC-HEADER>0001179110-04-016861.hdr.sgml : 20040820
<ACCEPTANCE-DATETIME>20040820103845
ACCESSION NUMBER:		0001179110-04-016861
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031203
FILED AS OF DATE:		20040820

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			KELLSTROM WILLIAM A
		CENTRAL INDEX KEY:			0001237512

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31239
		FILM NUMBER:		04987812

	BUSINESS ADDRESS:	
		STREET 1:		155 INVERNESS DRIVE WEST
		STREET 2:		SUITE 200
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80112
		BUSINESS PHONE:		303 290 8700

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MARKWEST ENERGY PARTNERS L P
		CENTRAL INDEX KEY:			0001166036
		STANDARD INDUSTRIAL CLASSIFICATION:	CRUDE PETROLEUM & NATURAL GAS [1311]
		IRS NUMBER:				270005456
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		155 INVERNESS DR WEST
		STREET 2:		STE 200
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80112
		BUSINESS PHONE:		303-925-9275

	MAIL ADDRESS:	
		STREET 1:		155 INVERNESS DR WEST
		STREET 2:		STE 200
		CITY:			ENGLEWOOD
		STATE:			CO
		ZIP:			80112
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-12-03</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001166036</issuerCik>
        <issuerName>MARKWEST ENERGY PARTNERS L P</issuerName>
        <issuerTradingSymbol>MWE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001237512</rptOwnerCik>
            <rptOwnerName>KELLSTROM WILLIAM A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MARKWEST ENERGY PARTNERS, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>155 INVERNESS DRIVE WEST, STE 200</rptOwnerStreet2>
            <rptOwnerCity>ENGLEWOOD</rptOwnerCity>
            <rptOwnerState>CO</rptOwnerState>
            <rptOwnerZipCode>80112</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable></nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Phantom Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2003-12-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F2"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Units</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>875</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">1 for 1</footnote>
        <footnote id="F2">Under the phantom unit grant agreement, the settlement of the phantom units occurs automatically as the phantom units vest, which results in a deemed automatic expiration of the vested portion of the phantom units upon settlement.  The phantom units vest generally over a period of four years, with 25% vesting at the end of the second and third years after the date of grant, and 50% vesting at the end of the fourth year after the date of grant.  The vesting may be accelerated in certain instances if the issuer achieves certain unitholder distribution targets.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Andy Schulz  POA for William Kellstrom</signatureName>
        <signatureDate>2004-08-11</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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