<Page>

      AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 25, 2002
                                                   REGISTRATION NO. 333-________

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                             ----------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                             ----------------------

                         MARKWEST ENERGY PARTNERS, L.P.
             (Exact name of registrant as specified in its charter)

               DELAWARE                                        27-0005456
    (State or other jurisdiction                            (I.R.S. Employer
  of incorporation or organization)                       Identification Number)

                       155 INVERNESS DRIVE WEST, SUITE 200
                            ENGLEWOOD, COLORADO 80112
               (Address, including zip code, and telephone number,
                 including area code, of registrant's principal
                     executive offices, including zip code)

                             ----------------------

             MARKWEST ENERGY PARTNERS, L.P. LONG-TERM INCENTIVE PLAN
                            (Full title of the plans)

                               GERALD A. TYWONIUK
                         MARKWEST ENERGY PARTNERS, L.P.
                       155 INVERNESS DRIVE WEST, SUITE 200
                            ENGLEWOOD, COLORADO 80112
                     (Name and address of agent for service)

                                 (303) 290-8700
          (Telephone number, including area code, of agent for service)

                                   COPIES TO:

                                 David P. Oelman
                               Jeffrey M. Cameron
                             Vinson & Elkins L.L.P.
                         1001 Fannin Street, Suite 2300
                            Houston, Texas 77002-6760
                                 (713) 758-2222

                         CALCULATION OF REGISTRATION FEE

<Table>
<Caption>
                                                          PROPOSED MAXIMUM       PROPOSED MAXIMUM       AMOUNT OF
         TITLE OF SECURITIES             AMOUNT TO BE      OFFERING PRICE       AGGREGATE OFFERING     REGISTRATION
          TO BE REGISTERED              REGISTERED(2)       PER UNIT(1)              PRICE(1)              FEE
--------------------------------------  --------------    ----------------      ------------------     ------------
<S>                                     <C>               <C>                   <C>                    <C>
Common units, representing limited      500,000 units          $21.19               $10,595,000          $974.74
partner interests, which may be
issued pursuant to the MarkWest
Energy Partners, L.P. Long-Term                                   -                      -
Incentive Plan......................
</Table>

(1)  Estimated solely for the purpose of computing the registration fee in
     accordance with paragraphs (c) and (h) of Rule 457 under the Securities Act
     of 1933 on the basis of the average high and low prices of the Common Units
     as reported on the American Stock Exchange on June 17, 2002.

(2)  Pursuant to Rule 416(c) under the Securities Act of 1933, as amended, this
     registration statement shall also cover any additional common units that
     become issuable under the plan by reason of any stock dividend, stock
     split, recapitalization or any other similar transaction effected without
     the receipt of consideration which results in an increase in the number of
     the registrant's outstanding common units.

================================================================================

<Page>

                                     PART I

     The document(s) containing the information specified in Part I of Form S-8
will be sent or given to participants as specified by Rule 428(b)(1) of the
Securities Act of 1933, as amended. Such documents and the documents
incorporated by reference herein pursuant to Item 3 of Part II hereof, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act of 1933, as amended.

                                     PART II
               INFORMATION REQUIRED IN THIS REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

     The following documents filed with the Commission are incorporated herein
by reference:

     (a)  The Registrant's Prospectus filed pursuant to Rule 424(b) on May 21,
          2002; and

     (b)  The description of the Registrant's Common Units contained in its
          Registration Statement on Form S-1, as amended (File No. 33-81780).

     In addition, all documents Registrant subsequently files pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), after the effective date of this Registration
Statement, and prior to the filing of a post-effective amendment to this
Registration Statement indicating that all securities offered hereby have been
sold or deregistering all securities then remaining unsold, shall be deemed to
be incorporated by reference and to be a part hereof from the date of filing of
such documents. Any statement contained herein or in any document incorporated
or deemed to be incorporated by reference shall be deemed to be modified or
superseded for purposes of this registration statement to the extent that a
statement contained in any other subsequently filed document which also is or is
deemed to be incorporated by reference modifies or supersedes such statement.
Any such statement so modified or superseded shall not be deemed to constitute a
part of this registration statement, except as so modified or superseded.

ITEM 4. DESCRIPTION OF SECURITIES.

     Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 17-108 of the Delaware Revised Uniform Limited Partnership Act
empowers a Delaware limited partnership to indemnify and hold harmless any
partner or other person from and against all claims and demands whatsoever.
Section 7.7(a) of the Amended and Restated Partnership Agreement of the
Partnership (the "Partnership Agreement") provides that to the fullest extent
permitted by law, (a) the General Partner, (b) any former General Partner (a
"Departing Partner"), (c) any individual, corporation, partnership, trust,
unincorporated organization, association or other entity (collectively, a
"Person") who is or was an affiliate of the General Partner or Departing
Partner, (d) Any Person who is or was a member, partner officer, director,
employee, agent or trustee of the General Partner, Departing Partner, the
Partnership, the Operating Company and any of their subsidiaries, and (e) any
Person who is or was serving at the request of the General Partner or any
Departing Partner or their affiliates as an officer, director, employee, member,
partner, agent, fiduciary or trustee of another Person (collectively the
"Indemnitees"), shall be indemnified and held harmless by the Partnership, from
and against any and all losses, claims, damages, liabilities, joint or several,
expenses (including legal fees and expenses), judgments, fines, penalties,
interest, settlements or other amounts arising from any and all claims, demands,
actions, suits or proceedings, whether civil, criminal, administrative or
investigative, in which any Indemnitee may be involved, or is threatened to be
involved, as a party or otherwise, by reason of its status as an Indemnitee;
provided, that in each case the Indemnitee acted in good faith, in a manner that
such Indemnitee reasonably believed to be in, or (in the case of a Person other
than the General Partner) not opposed to, the best interests of the Partnership
and, with respect to any criminal proceeding, had no reasonable cause to believe
its conduct was unlawful; provided, further, no indemnification pursuant to
Section 7.7 of the Partnership Agreement shall be available to the General
Partner of

                                       2
<Page>

its Affiliates (other than a Group Member) with respect to its or their
obligations incurred pursuant to the Underwriting Agreement or the Contribution
Agreement (other than obligations incurred by the General Partner on behalf of
the Partnership). The termination of any action, suit or proceeding by judgment,
order, settlement, conviction or upon a plea of nolo contendere, or its
equivalent, shall not create a presumption that the Indemnitee acted in a manner
contrary to that specified above. Any indemnification pursuant to Section 7.7 of
the Partnership Agreement shall be made only out of the assets of the
Partnership, it being agreed that the General Partner shall not be personally
liable for such indemnification and shall have no obligation to contribute or
loan any monies or property to the Partnership to enable it to effectuate such
indemnification.

     Section 7.7(b) of the Partnership Agreement also states that to the fullest
extent permitted by law, expenses (including without limitation, reasonable
legal fees and expenses) incurred by an indemnitee in defending any claim,
demand action, suit or proceeding shall, from time to time, be advanced by the
Partnership prior to the final disposition of such claim, demand, action, suit
or proceeding upon receipt by the Partnership of an undertaking by or on behalf
of the indemnitee to repay such amount if it shall be determined that the
indemnitee is not entitled to be indemnified as authorized by the Partnership
Agreement.

     Additionally, Section 7.8(b) of the Partnership Agreement provides that no
indemnitee shall be liable for monetary damages to the Partnership, the limited
partners of the Partnership, the assignees or any other Persons who have
acquired interests in common or preference units of the Partnership, for losses
sustained or liabilities incurred as a result of any act or omission if such
indemnitee acted in good faith.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

     Not applicable.

ITEM 8. EXHIBITS.

     Reference is made to the Exhibit Index which appears at page 7 of this
Registration Statement for a detailed list of exhibits filed as a part hereof.

ITEM 9. UNDERTAKINGS.

     (a)  The undersigned registrant hereby undertakes:

          (1)  To file, during any period in which offers or sales are being
     made, a post-effective amendment to this registration statement:

               (i)  To include any prospectus required by Section 10(a)(3) of
          the Securities Act of 1933;

               (ii) To reflect in the prospectus any facts or events arising
          after the effective date of this registration statement (or the most
          recent post-effective amendment thereof) which, individually or in the
          aggregate, represent a fundamental change in the information set forth
          in this registration statement. Notwithstanding the foregoing, any
          increase or decrease in volume of the securities offered (if the total
          dollar value of securities offered would not exceed that which was
          registered) and any deviation from the low or high end of the
          estimated maximum offering range may be reflected in the form of
          prospectus filed with the Commission pursuant to Rule 424(b) if, in
          the aggregate, the changes in volume and price represent no more than
          a 20 percent change in the maximum aggregate offering price set forth
          in the "Calculation of Registration Fee" table in the effective
          registration statement;

               (iii) To include any material information with respect to the
          plan of distribution not previously disclosed in this registration
          statement or any material change to such information in this
          registration statement;

PROVIDED, HOWEVER, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed by the registrant pursuant to
Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are
incorporated by reference in this registration statement.

                                       3
<Page>

         (2) That, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new registration statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial BONA FIDE offering thereof.

         (3) To remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

     (b)  That, for the purposes of determining any liability under the
Securities Act of 1933, each filing of the registrant's annual report pursuant
to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and,
where applicable, each filing of an employee benefit plan's annual report
pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is
incorporated by reference in this registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial BONA
FIDE offering thereof.

     (c)  Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                       4
<Page>

                                   SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the
registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned,
thereunto duly authorized, in the City of Englewood, State of Colorado, on
the 25th day of June, 2002.

                                        MARKWEST ENERGY PARTNERS, L.P.

                                        By: MarkWest Energy GP, L.L.C.,
                                               its general partner

                                        By: /s/ Gerald A. Tywoniuk
                                            --------------------------------
                                            Gerald A. Tywoniuk
                                            Senior Vice President and
                                            Chief Financial Officer


     Each person whose signature appears below appoints Arthur J. Denney and
Gerald M. Tywoniuk, and each of them, with full power of substitution, their
true and lawful attorneys-in-fact and agents to do any and all acts and things
in the undersigned's name and on the undersigned's behalf in the undersigned's
capacity as an officer or director of MarkWest Energy GP, L.L.C. in connection
with, and only in connection with, the filing of this registration statement
(including, but not limited to, the execution of any and all instruments for the
undersigned in the undersigned's name which such person may deem necessary or
advisable to enable MarkWest Energy Partners, L.P. to comply with the Securities
Act of 1933, as amended (the "Act") and rules, regulations and requirements of
the Securities and Exchange Commission, in connection with the filing of this
registration statement), including specifically, but not limited to, the power
and authority to sign for the undersigned any and all amendments, including
post-effective amendments; and the undersigned does hereby ratify and confirm
all that such person or persons shall do or cause to be done by virtue hereof.

     Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.


      SIGNATURE                          TITLE                          DATE


/s/ John M. Fox            Chairman of the Board of Directors,     June 25, 2002
------------------------   President and Chief Executive Officer
    John M. Fox            (Principal Executive Officer)


/s/ Gerald A. Tywoniuk     Senior Vice President and Chief         June 25, 2002
------------------------   Financial Officer (Principal Financial
    Gerald A. Tywoniuk     and Accounting Officer) and Director


/s/ Arthur J. Denney
------------------------   Executive Vice President and Director   June 25, 2002
    Arthur J. Denney


/s/ Donald C. Heppermann
------------------------   Director                                June 25, 2002
    Donald C. Heppermann

/s/ William A. Kellstrom
------------------------   Director                                June 25, 2002
    William A. Kellstrom

/s/ William P. Nicoletti
------------------------   Director                                June 25, 2002
    William P. Nicoletti


                                       5
<Page>

                                INDEX TO EXHIBITS

<Table>
<Caption>
Exhibit
 Number   Description
-------   -----------
<S>       <C>
4.1    -  Form of Amended and Restated Agreement of Limited Partnership of
          MarkWest Energy Partners, L.P. (filed as Appendix A to Prospectus
          filed pursuant to Rule 424(b) on May 22, 2002 and incorporated herein
          by reference).

4.2    -  Form of Amended and Restated Limited Liability Company Agreement of
          MarkWest Energy GP, L.L.C. (previously filed with Amendment No. 3 to
          the Registration Statement on Form S-1 (File No. 333-81780) on April
          25, 2002 and incorporated herein by reference).

5.1    -  Opinion of Vinson & Elkins L.L.P. as to the validity of the securities
          being registered.

10.1   -  MarkWest Energy Partners, L.P. Long-Term Incentive Plan (previously
          filed with Amendment No. 1 to the Registration Statement on Form S-1
          (File No. 333-81780) on March 22, 2002 and incorporated herein by
          reference).

10.2   -  First Amendment to the MarkWest Energy Partners, L.P. Long-Term
          Incentive Plan (previously filed as Exhibit 10.4 to the Current Report
          on Form 8-K on June 7, 2002 and incorporated herein by reference).

23.1   -  Consent of Vinson & Elkins L.L.P. (included in Exhibit 5.1).

24.1   -  Power of Attorney (set forth on the signature page contained in Part
          II of this Registration Statement).
</Table>


                                       6
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{"company-data": {"conformed-name": "MARKWEST ENERGY PARTNERS L P", "cik": "0001166036", "assigned-sic": "1311", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-91120", "film-number": "02686453"}, "business-address": {"street1": "155 INVERNESS DR WEST", "street2": "STE 200", "city": "ENGLEWOOD", "state": "CO", "zip": "80112", "phone": "3032908700"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 25, 2002
                                                   REGISTRATION NO. 333-________

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                             ----------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                             ----------------------

                         MARKWEST ENERGY PARTNERS, L.P.
             (Exact name of registrant as specified in its charter)

               DELAWARE                                        27-0005456
    (State or other jurisdiction                            (I.R.S. Employer
  of incorporation or organization)                       Identification Number)

                       155 INVERNESS DRIVE WEST, SUITE 200
                            ENGLEWOOD, COLORADO 80112
               (Address, including zip code, and telephone number,
                 including area code, of registrant's principal
                     executive offices, including zip code)

                             ----------------------

             MARKWEST ENERGY PARTNERS, L.P. LONG-TERM INCENTIVE PLAN
                            (Full title of the plans)

                               GERALD A. TYWONIUK
                         MARKWEST ENERGY PARTNERS, L.P.
                       155 INVERNESS DRIVE WEST, SUITE 200
                            ENGLEWOOD, COLORADO 80112
                     (Name and address of agent for service)

                                 (303) 290-8700
          (Telephone number, including area code, of agent for service)

                                   COPIES TO:

                                 David P. Oelman
                               Jeffrey M. Cameron
                             Vinson & Elkins L.L.P.
                         1001 Fannin Street, Suite 2300
                            Houston, Texas 77002-6760
                                 (713) 758-2222

                         CALCULATION OF REGISTRATION FEE
PROPOSED MAXIMUM       PROPOSED MAXIMUM       AMOUNT OF
         TITLE OF SECURITIES             AMOUNT TO BE      OFFERING PRICE       AGGREGATE OFFERING     REGISTRATION
          TO BE REGISTERED              REGISTERED(2)       PER UNIT(1)              PRICE(1)              FEE
--------------------------------------  --------------    ----------------      ------------------     ------------
Common units, representing limited      500,000 units          $21.19               $10,595,000          $974.74
partner interests, which may be
issued pursuant to the MarkWest
Energy Partners, L.P. Long-Term                                   -                      -
Incentive Plan......................
(1)  Estimated solely for the purpose of computing the registration fee in
     accordance with paragraphs (c) and (h) of Rule 457 under the Securities Act
     of 1933 on the basis of the average high and low prices of the Common Units
     as reported on the American Stock Exchange on June 17, 2002.

(2)  Pursuant to Rule 416(c) under the Securities Act of 1933, as amended, this
     registration statement shall also cover any additional common units that
     become issuable under the plan by reason of any stock dividend, stock
     split, recapitalization or any other similar transaction effected without
     the receipt of consideration which results in an increase in the number of
     the registrant's outstanding common units.

================================================================================
PART I

     The document(s) containing the information specified in Part I of Form S-8
will be sent or given to participants as specified by Rule 428(b)(1) of the
Securities Act of 1933, as amended. Such documents and the documents
incorporated by reference herein pursuant to Item 3 of Part II hereof, taken
together, constitute a prospectus that meets the requirements of Section 10(a)
of the Securities Act of 1933, as amended.

                                     PART II
               INFORMATION REQUIRED IN THIS REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF DOCUMENTS BY REFERENCE.

     The following documents filed with the Commission are incorporated herein
by reference:

     (a)  The Registrant's Prospectus filed pursuant to Rule 424(b) on May 21,
          2002; and

     (b)  The description of the Registrant's Common Units contained in its
          Registration Statement on Form S-1, as amended (File No. 33-81780).

     In addition, all documents Registrant subsequently files pursuant to
Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), after the effective date of this Registration
Statement, and prior to the filing of a post-effective amendment to this
Registration Statement indicating that all securities offered hereby have been
sold or deregistering all securities then remaining unsold, shall be deemed to
be incorporated by reference and to be a part hereof from the date of filing of
such documents. Any statement contained herein or in any document incorporated
or deemed to be incorporated by reference shall be deemed to be modified or
superseded for purposes of this registration statement to the extent that a
statement contained in any other subsequently filed document which also is or is
deemed to be incorporated by reference modifies or supersedes such statement.
Any such statement so modified or superseded shall not be deemed to constitute a
part of this registration statement, except as so modified or superseded.

ITEM 4. DESCRIPTION OF SECURITIES.

     Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

ITEM 6. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Section 17-108 of the Delaware Revised Uniform Limited Partnership Act
empowers a Delaware limited partnership to indemnify and hold harmless any
partner or other person from and against all claims and demands whatsoever.
Section 7.7(a) of the Amended and Restated Partnership Agreement of the
Partnership (the "Partnership Agreement") provides that to the fullest extent
permitted by law, (a) the General Partner, (b) any former General Partner (a
"Departing Partner"), (c) any individual, corporation, partnership, trust,
unincorporated organization, association or other entity (collectively, a
"Person") who is or was an affiliate of the General Partner or Departing
Partner, (d) Any Person who is or was a member, partner officer, director,
employee, agent or trustee of the General Partner, Departing Partner, the
Partnership, the Operating Company and any of their subsidiaries, and (e) any
Person who is or was serving at the request of the General Partner or any
Departing Partner or their affiliates as an officer, director, employee, member,
partner, agent, fiduciary or trustee of another Person (collectively the
"Indemnitees"), shall be indemnified and held harmless by the Partnership, from
and against any and all losses, claims, damages, liabilities, joint or several,
expenses (including legal fees and expenses), judgments, fines, penalties,
interest, settlements or other amounts arising from any and all claims, demands,
actions, suits or proceedings, whether civil, criminal, administrative or
investigative, in which any Indemnitee may be involved, or is threatened to be
involved, as a party or otherwise, by reason of its status as an Indemnitee;
provided, that in each case the Indemnitee acted in good faith, in a manner that
such Indemnitee reasonably believed to be in, or (in the case of a Person other
than the General Partner) not opposed to, the best interests of the Partnership
and, with respect to any criminal proceeding, had no reasonable cause to believe
its conduct was unlawful; provided, further, no indemnification pursuant to
Section 7.7 of the Partnership Agreement shall be available to the General
Partner of

                                       2
its Affiliates (other than a Group Member) with respect to its or their
obligations incurred pursuant to the Underwriting Agreement or the Contribution
Agreement (other than obligations incurred by the General Partner on behalf of
the Partnership). The termination of any action, suit or proceeding by judgment,
order, settlement, conviction or upon a plea of nolo contendere, or its
equivalent, shall not create a presumption that the Indemnitee acted in a manner
contrary to that specified above. Any indemnification pursuant to Section 7.7 of
the Partnership Agreement shall be made only out of the assets of the
Partnership, it being agreed that the General Partner shall not be personally
liable for such indemnification and shall have no obligation to contribute or
loan any monies or property to the Partnership to enable it to effectuate such
indemnification.

     Section 7.7(b) of the Partnership Agreement also states that to the fullest
extent permitted by law, expenses (including without limitation, reasonable
legal fees and expenses) incurred by an indemnitee in defending any claim,
demand action, suit or proceeding shall, from time to time, be advanced by the
Partnership prior to the final disposition of such claim, demand, action, suit
or proceeding upon receipt by the Partnership of an undertaking by or on behalf
of the indemnitee to repay such amount if it shall be determined that the
indemnitee is not entitled to be indemnified as authorized by the Partnership
Agreement.

     Additionally, Section 7.8(b) of the Partnership Agreement provides that no
indemnitee shall be liable for monetary damages to the Partnership, the limited
partners of the Partnership, the assignees or any other Persons who have
acquired interests in common or preference units of the Partnership, for losses
sustained or liabilities incurred as a result of any act or omission if such
indemnitee acted in good faith.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED.

     Not applicable.

ITEM 8. EXHIBITS.

     Reference is made to the Exhibit Index which appears at page 7 of this
Registration Statement for a detailed list of exhibits filed as a part hereof.

ITEM 9. UNDERTAKINGS.

     (a)  The undersigned registrant hereby undertakes:

          (1)  To file, during any period in which offers or sales are being
     made, a post-effective amendment to this registration statement:

               (i)  To include any prospectus required by Section 10(a)(3) of
          the Securities Act of 1933;

               (ii) To reflect in the prospectus any facts or events arising
          after the effective date of this registration statement (or the most
          recent post-effective amendment thereof) which, individually or in the
          aggregate, represent a fundamental change in the information set forth
          in this registration statement. Notwithstanding the foregoing, any
          increase or decrease in volume of the securities offered (if the total
          dollar value of securities offered would not exceed that which was
          registered) and any deviation from the low or high end of the
          estimated maximum offering range may be reflected in the form of
          prospectus filed with the Commission pursuant to Rule 424(b) if, in
          the aggregate, the changes in volume and price represent no more than
          a 20 percent change in the maximum aggregate offering price set forth
          in the "Calculation of Registration Fee" table in the effective
          registration statement;

               (iii) To include any material information with respect to the
          plan of distribution not previously disclosed in this registration
          statement or any material change to such information in this
          registration statement;

PROVIDED, HOWEVER, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed by the registrant pursuant to
Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are
incorporated by reference in this registration statement.

                                       3
(2) That, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new registration statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial BONA FIDE offering thereof.

         (3) To remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

     (b)  That, for the purposes of determining any liability under the
Securities Act of 1933, each filing of the registrant's annual report pursuant
to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and,
where applicable, each filing of an employee benefit plan's annual report
pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is
incorporated by reference in this registration statement shall be deemed to be a
new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial BONA
FIDE offering thereof.

     (c)  Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                       4
SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the
registrant certifies that it has reasonable grounds to believe that it meets
all of the requirements for filing on Form S-8 and has duly caused this
registration statement to be signed on its behalf by the undersigned,
thereunto duly authorized, in the City of Englewood, State of Colorado, on
the 25th day of June, 2002.

                                        MARKWEST ENERGY PARTNERS, L.P.

                                        By: MarkWest Energy GP, L.L.C.,
                                               its general partner

                                        By: /s/ Gerald A. Tywoniuk
                                            --------------------------------
                                            Gerald A. Tywoniuk
                                            Senior Vice President and
                                            Chief Financial Officer

     Each person whose signature appears below appoints Arthur J. Denney and
Gerald M. Tywoniuk, and each of them, with full power of substitution, their
true and lawful attorneys-in-fact and agents to do any and all acts and things
in the undersigned's name and on the undersigned's behalf in the undersigned's
capacity as an officer or director of MarkWest Energy GP, L.L.C. in connection
with, and only in connection with, the filing of this registration statement
(including, but not limited to, the execution of any and all instruments for the
undersigned in the undersigned's name which such person may deem necessary or
advisable to enable MarkWest Energy Partners, L.P. to comply with the Securities
Act of 1933, as amended (the "Act") and rules, regulations and requirements of
the Securities and Exchange Commission, in connection with the filing of this
registration statement), including specifically, but not limited to, the power
and authority to sign for the undersigned any and all amendments, including
post-effective amendments; and the undersigned does hereby ratify and confirm
all that such person or persons shall do or cause to be done by virtue hereof.

     Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.

      SIGNATURE                          TITLE                          DATE

/s/ John M. Fox            Chairman of the Board of Directors,     June 25, 2002
------------------------   President and Chief Executive Officer
    John M. Fox            (Principal Executive Officer)

/s/ Gerald A. Tywoniuk     Senior Vice President and Chief         June 25, 2002
------------------------   Financial Officer (Principal Financial
    Gerald A. Tywoniuk     and Accounting Officer) and Director

/s/ Arthur J. Denney
------------------------   Executive Vice President and Director   June 25, 2002
    Arthur J. Denney

/s/ Donald C. Heppermann
------------------------   Director                                June 25, 2002
    Donald C. Heppermann

/s/ William A. Kellstrom
------------------------   Director                                June 25, 2002
    William A. Kellstrom

/s/ William P. Nicoletti
------------------------   Director                                June 25, 2002
    William P. Nicoletti

                                       5
INDEX TO EXHIBITS
Exhibit
 Number   Description
-------   -----------
4.1    -  Form of Amended and Restated Agreement of Limited Partnership of
          MarkWest Energy Partners, L.P. (filed as Appendix A to Prospectus
          filed pursuant to Rule 424(b) on May 22, 2002 and incorporated herein
          by reference).

4.2    -  Form of Amended and Restated Limited Liability Company Agreement of
          MarkWest Energy GP, L.L.C. (previously filed with Amendment No. 3 to
          the Registration Statement on Form S-1 (File No. 333-81780) on April
          25, 2002 and incorporated herein by reference).

5.1    -  Opinion of Vinson & Elkins L.L.P. as to the validity of the securities
          being registered.

10.1   -  MarkWest Energy Partners, L.P. Long-Term Incentive Plan (previously
          filed with Amendment No. 1 to the Registration Statement on Form S-1
          (File No. 333-81780) on March 22, 2002 and incorporated herein by
          reference).

10.2   -  First Amendment to the MarkWest Energy Partners, L.P. Long-Term
          Incentive Plan (previously filed as Exhibit 10.4 to the Current Report
          on Form 8-K on June 7, 2002 and incorporated herein by reference).

23.1   -  Consent of Vinson & Elkins L.L.P. (included in Exhibit 5.1).

24.1   -  Power of Attorney (set forth on the signature page contained in Part
          II of this Registration Statement).
6