MarkWest Energy Partners, LP (MWE)

ASSIGNMENT OF COMMON UNITS
 in
 MARKWEST ENERGY PARTNERS, L.P.
 IMPORTANT NOTICE REGARDING INVESTOR RESPONSIBILITIES
 DUE TO TAX SHELTER STATUS OF
 MARKWEST ENERGY PARTNERS, L.P.

You have acquired an interest in MarkWest Energy Partners, L.P., 1515 Arapahoe Street, Tower 2, Suite 700, Denver, Colorado 80202, whose taxpayer identification number is 27-0005456.  The Internal Revenue Service has issued MarkWest Energy Partners, L.P. the following tax shelter registration number:02184000024.

YOU MUST REPORT THIS REGISTRATION NUMBER TO THE INTERNAL REVENUE SERVICE IF YOU CLAIM ANY DEDUCTION, LOSS, CREDIT OR OTHER TAX BENEFIT OR REPORT ANY INCOME BY REASON OF YOUR INVESTMENT IN MARKWEST ENERGY PARTNERS, L.P.

You must report the registration number as well as the name and taxpayer identification number of MarkWest Energy Partners, L.P. on Form 8271.  FORM 8271 MUST BE ATTACHED TO THE RETURN ON WHICH YOU CLAIM THE DEDUCTION, LOSS, CREDIT OR OTHER TAX BENEFIT OR REPORT ANY INCOME BY REASON OF YOUR INVESTMENT IN MARKWEST ENERGY PARTNERS, L.P.

If you transfer your interest in MarkWest Energy Partners, L.P. to another person, you are required by the Internal Revenue Service to keep a list containing (a) that person’s name, address and taxpayer identification number, (b) the date on which you transferred the interest and (c) the name, address and tax shelter registration number of MarkWest Energy Partners, L.P.  If you do not want to keep such a list, you must (1) send the information specified above to the Partnership, which will keep the list for this tax shelter, and (2) give a copy of this notice to the person to whom you transfer your interest.  Your failure to comply with any of the above-described responsibilities could result in the imposition of a penalty under Section 6707(b) or 6708(a) of the Internal Revenue Code of 1986, as amended, unless such failure is shown to be due to reasonable cause.

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ASSIGNMENT OF COMMON UNITS
in
MARKWEST ENERGY PARTNERS, L.P.
IMPORTANT NOTICE REGARDING INVESTOR RESPONSIBILITIES
DUE TO TAX SHELTER STATUS OF
MARKWEST ENERGY PARTNERS, L.P.

        You have acquired an interest in MarkWest Energy Partners, L.P., 155 Inverness Drive West, Suite 200, Englewood, Colorado 80112, whose taxpayer identification number is 20-0005456. The Internal Revenue Service has issued MarkWest Energy Partners, L.P. the following tax shelter registration number:                        .

        YOU MUST REPORT THIS REGISTRATION NUMBER TO THE INTERNAL REVENUE SERVICE IF YOU CLAIM ANY DEDUCTION, LOSS, CREDIT OR OTHER TAX BENEFIT OR REPORT ANY INCOME BY REASON OF YOUR INVESTMENT IN MARKWEST ENERGY PARTNERS, L.P.

        You must report the registration number as well as the name and taxpayer identification number of MarkWest Energy Partners, L.P. on Form 8271. FORM 8271 MUST BE ATTACHED TO THE RETURN ON WHICH YOU CLAIM THE DEDUCTION, LOSS, CREDIT OR OTHER TAX BENEFIT OR REPORT ANY INCOME BY REASON OF YOUR INVESTMENT IN MARKWEST ENERGY PARTNERS, L.P.

        If you transfer your interest in MarkWest Energy Partners, L.P. to another person, you are required by the Internal Revenue Service to keep a list containing (a) that person's name, address and taxpayer identification number, (b) the date on which you transferred the interest and (c) the name, address and tax shelter registration number of MarkWest Energy Partners, L.P. If you do not want to keep such a list, you must (1) send the information specified above to the Partnership, which will keep the list for this tax shelter, and (2) give a copy of this notice to the person to whom you transfer your interest. Your failure to comply with any of the above-described responsibilities could result in the imposition of a penalty under Section 6707(b) or 6708(a) of the Internal Revenue Code of 1986, as amended, unless such failure is shown to be due to reasonable cause.

        ISSUANCE OF A REGISTRATION NUMBER DOES NOT INDICATE THAT THIS INVESTMENT OR THE CLAIMED TAX BENEFITS HAVE BEEN REVIEWED, EXAMINED OR APPROVED BY THE INTERNAL REVENUE SERVICE.

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        FOR VALUE RECEIVED,                        hereby assigns, conveys, sells and transfers unto

Common Units representing limited partner interests evidenced by this Certificate, subject to the Partnership Agreement, and does hereby irrevocably constitute and appoint                        as its attorney-in-fact with full power of substitution to transfer the same on the books of MarkWest Energy Partners, L.P.

        No transfer of the Common Units evidenced hereby will be registered on the books of the Partnership, unless the Certificate evidencing the Common Units to be transferred is surrendered for registration or transfer and an Application for Transfer of Common Units has been executed by a transferee either (a) on the form set forth below or (b) on a separate application that the Partnership will furnish on request without charge. A transferor of the Common Units shall have no duty to the transferee with respect to execution of the transfer application in order for such transferee to obtain registration of the transfer of the Common Units.

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APPLICATION FOR TRANSFER OF COMMON UNITS

        The undersigned ("Assignee") hereby applies for transfer to the name of the Assignee of the Common Units evidenced hereby.

        The Assignee (a) requests admission as a Substituted Limited Partner and agrees to comply with and be bound by, and hereby executes, the Amended and Restated Agreement of Limited Partnership of MarkWest Energy Partners, L.P. (the "Partnership"), as amended, supplemented or restated to the date hereof (the "Partnership Agreement"), (b) represents and warrants that the Assignee has all right, power and authority and, if an individual, the capacity necessary to enter into the Partnership Agreement, (c) appoints the General Partner of the Partnership and, if a Liquidator shall be appointed, the Liquidator of the Partnership as the Assignee's attorney-in-fact to execute, swear to, acknowledge and file any document, including, without limitation, the Partnership Agreement and any amendment thereto and the Certificate of Limited Partnership of the Partnership and any amendment thereto, necessary or appropriate for the Assignee's admission as a Substituted Limited Partner and as a party to the Partnership Agreement, (d) gives the powers of attorney provided for in the Partnership Agreement, and (e) makes the waivers and gives the consents and approvals contained in the Partnership Agreement. Capitalized terms not defined herein have the meanings assigned to such terms in the Partnership Agreement.

Type of Entity (check one):

Nationality (check one):

        If the U.S. Citizen, Resident or Domestic Entity box is checked, the following certification must be completed.

        Under Section 1445(e) of the Internal Revenue Code of 1986, as amended (the "Code"), the Partnership must withhold tax with respect to certain transfers of property if a holder of an interest in the Partnership is a foreign person. To inform the Partnership that no withholding is required with respect to the undersigned interestholder's interest in it, the undersigned hereby certifies the following (or, if applicable, certifies the following on behalf of the interestholder).

Complete Either A or B:

A.

Individual Interestholder

        1.     I am not a non-resident alien for purposes of U.S. income taxation.

        2.     My U.S. taxpayer identification number (Social Security Number) is                        .

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        3.     My home address is                        .

B.

Partnership, Corporation or Other Interestholder

        1.                             is not a foreign corporation, foreign partnership, foreign trust (Name of Interestholder) or foreign estate (as those terms are defined in the Code and Treasury Regulations).

        2.     The interestholder's U.S. employer identification number is                        .

        3.     The interestholder's office address and place of incorporation (if applicable) is                        .

        The interestholder agrees to notify the Partnership within sixty (60) days of the date the interestholder becomes a foreign person.

        The interestholder understands that this certificate may be disclosed to the Internal Revenue Service by the Partnership and that any false statement contained herein could be punishable by fine, imprisonment or both.

        Under penalties of perjury, I declare that I have examined this certification and to the best of my knowledge and belief it is true, correct and complete and, if applicable, I further declare that I have authority to sign this document on behalf of:

        Note:    If the Assignee is a broker, dealer, bank, trust company, clearing corporation, other nominee holder or an agent of any of the foregoing, and is holding for the account of any other person, this application should be completed by an officer thereof or, in the case of a broker or dealer, by a registered representative who is a member of a registered national securities exchange or a member of the National Association of Securities Dealers, Inc., or, in the case of any other nominee holder, a person performing a similar function. If the Assignee is a broker, dealer, bank, trust company, clearing corporation, other nominee owner or an agent of any of the foregoing, the above certification as to any person for whom the Assignee will hold the Common Units shall be made to the best of the Assignee's knowledge.

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Annex B

ASSIGNMENT OF COMMON UNITS
in
MARKWEST ENERGY PARTNERS, L.P.
IMPORTANT NOTICE REGARDING INVESTOR RESPONSIBILITIES
DUE TO TAX SHELTER STATUS OF
MARKWEST ENERGY PARTNERS, L.P.

You have acquired an interest in MarkWest EnergyPartners, L.P., 155 Inverness Drive West, Suite 200, Englewood, Colorado 80112, whose taxpayer identification number is [         ].  The Internal Revenue Service has issued MarkWest EnergyPartners, L.P. the following tax shelter registration number:             .

YOU MUST REPORT THIS REGISTRATION NUMBER TO THE INTERNAL REVENUE SERVICE IF YOU CLAIM ANY DEDUCTION, LOSS, CREDIT OR OTHER TAX BENEFIT OR REPORT ANY INCOME BY REASON OF YOUR INVESTMENT IN MARKWEST ENERGY PARTNERS, L.P.

You must report the registration number as well as the name and taxpayer identification number of MarkWest Energy Partners, L.P. on Form 8271.  FORM 8271 MUST BE ATTACHED TO THE RETURN ON WHICH YOU CLAIM THE DEDUCTION, LOSS, CREDIT OR OTHER TAX BENEFIT OR REPORT ANY INCOME BY REASON OF YOUR INVESTMENT IN MARKWEST ENERGY PARTNERS, L.P.

If you transfer your interest in MarkWest EnergyPartners, L.P. to another person, you are required by the Internal Revenue Service to keep a list containing (a) that person’s name, address and taxpayer identification number, (b) the date on which you transferred the interest and (c) the name, address and tax shelter registration number of MarkWest EnergyPartners, L.P.  If you do not want to keep such a list, you must (1) send the information specified above to the Partnership, which will keep the list for this tax shelter, and (2) give a copy of this notice to the person to whom you transfer your interest.  Your failure to comply with any of the above-described responsibilities could result in the imposition of a penalty under Section 6707(b) or

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6708(a) of the Internal Revenue Code of 1986, as amended, unless such failure is shown to be due to reasonable cause.

ISSUANCE OF A REGISTRATION NUMBER DOES NOT INDICATE THAT THIS INVESTMENT OR THE CLAIMED TAX BENEFITS HAVE BEEN REVIEWED, EXAMINED OR APPROVED BY THE INTERNAL REVENUE SERVICE.

FOR VALUE RECEIVED,              hereby assigns, conveys, sells and transfers unto

             Common Units representing limited partner interests evidenced by this Certificate, subject to the Partnership Agreement, and does hereby irrevocably constitute and appoint              as its attorney-in-fact with full power of substitution to transfer the same on the books of MarkWest EnergyPartners, L.P.

No transfer of the Common Units evidenced hereby will be registered on the books of the Partnership, unless the Certificate evidencing the Common Units to be transferred is surrendered for registration or transfer and an Application for Transfer of Common Units has been executed by a transferee either (a) on the form set forth below or (b) on a separate application that the Partnership will furnish on request without charge.  A transferor of the Common Units shall have no duty to the transferee with respect to execution of the transfer application in order for such transferee to obtain registration of the transfer of the Common Units.

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