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                                                                    EXHIBIT 10.3

                         MARKWEST ENERGY PARTNERS, L.P.
                            LONG-TERM INCENTIVE PLAN

SECTION 1. PURPOSE OF THE PLAN.

     The MarkWest Energy Partners, L.P. Long-Term Incentive Plan (the "Plan") is
intended to promote the interests of MarkWest Energy Partners, L.P., a Delaware
limited partnership (the "Partnership"), by providing to employees and directors
of MarkWest Energy GP, L.L.C. (the "Company") and its Affiliates who perform
services for the Partnership incentive compensation awards for superior
performance that are based on Units. The Plan is also contemplated to enhance
the ability of the Company and its Affiliates to attract and retain the services
of individuals who are essential for the growth and profitability of the
Partnership and to encourage them to devote their best efforts to the business
of the Partnership, thereby advancing the interests of the Partnership and its
partners.

SECTION 2. DEFINITIONS.

     As used in the Plan, the following terms shall have the meanings set forth
below:

     "Affiliate" means, with respect to any Person, any other Person that
directly or indirectly through one or more intermediaries controls, is
controlled by or is under common control with, the Person in question. As used
herein, the term "control" means the possession, direct or indirect, of the
power to direct or cause the direction of the management and policies of a
Person, whether through ownership of voting securities, by contract or
otherwise.

     "Award" means an Option or Phantom Unit granted under the Plan, and shall
include any tandem DERs granted with respect to a Phantom Unit.

     "Board" means the Board of Directors of the Company.

     "Change in Control" shall be deemed to have occurred upon the occurrence of
one or more of the following events: (i) any sale, lease, exchange or other
transfer (in one or a series of related transactions) of all or substantially
all of the assets of the Partnership or the Company to any Person or its
Affiliates, other than the Partnership, the Company or any of their Affiliates,
(ii) any merger, reorganization, consolidation or other transaction pursuant to
which more than 50% of the combined voting power of the equity interests in the
Company ceases to be owned by Persons who own such interests as of the initial
public offering date of the Units, (iii) a "change of control" of MarkWest
Hydrocarbon, Inc., as provided in its 1997 Severance Plan, or (iv) the general
partner (whether the Company or any other Person) of the Partnership ceases to
be an Affiliate of MarkWest Hydrocarbon, Inc.

     "Committee" means the Compensation Committee of the Board or such other
committee of the Board appointed by the Board to administer the Plan.

     "DER" means a right, granted in tandem with a specific Phantom Unit, to
receive an amount in cash equal to, and at the same time as, the cash
distributions made by the Partnership with respect to a Unit during the period
such Phantom Unit is outstanding.

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     "Director" means a member of the Board who is not also an Employee.

     "Employee" means any employee of the Company or an Affiliate, as determined
by the Committee.

     "Exchange Act" means the Securities Exchange Act of 1934, as amended.

     "Fair Market Value" means the closing sales price of a Unit on the
applicable date (or if there is no trading in the Units on such date, the
closing sales price on the last date Units were traded) as reported in The Wall
Street Journal (or other reporting service approved by the Committee). In the
event Units are not publicly traded at the time a determination of fair market
value is required to be made hereunder, the determination of fair market value
shall be made in good faith by the Committee.

     "Option" means an option to purchase Units granted under the Plan.

     "Participant" means any Employee or Director granted an Award under the
Plan.

     "Partnership Agreement" means the Amended and Restated Agreement of Limited
Partnership of MarkWest Energy Partners, L.P.

     "Person" means an individual or a corporation, limited liability company,
partnership, joint venture, trust, unincorporated organization, association,
government agency or political subdivision thereof or other entity.

     "Phantom Unit" means a phantom (notional) Unit granted under the Plan which
upon vesting entitles the Participant to receive a Unit or an amount of cash
equal to the Fair Market Value of a Unit, whichever is determined by the
Committee.

     "Restricted Period" means the period established by the Committee with
respect to an Award during which the Award remains subject to forfeiture (is not
vested) and is not exercisable by or payable to the Participant.

     "Rule 16b-3" means Rule 16b-3 promulgated by the SEC under the Exchange
Act, or any successor rule or regulation thereto as in effect from time to time.

     "SEC" means the Securities and Exchange Commission, or any successor
thereto.

     "Unit" means a Common Unit of the Partnership.

SECTION 3. ADMINISTRATION.

     The Plan shall be administered by the Committee. A majority of the
Committee shall constitute a quorum, and the acts of the members of the
Committee who are present at any meeting thereof at which a quorum is present,
or acts unanimously approved by the members of the Committee in writing, shall
be the acts of the Committee. Subject to the following and any applicable law,
the Committee, in its sole discretion, may delegate any or all of its powers and
duties

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under the Plan, including the power to grant Awards under the Plan, to the Chief
Executive Officer of the Company (provided the Chief Executive Officer is a
member of the Board), subject to such limitations on such delegated powers and
duties as the Committee may impose, if any. Upon any such delegation all
references in the Plan to the "Committee", other than in Section 7, shall be
deemed to include the Chief Executive Officer; provided, however, that such
delegation shall not limit the Chief Executive Officer's right to receive Awards
under the Plan. Notwithstanding the foregoing, the Chief Executive Officer may
not grant Awards to, or take any action with respect to any Award previously
granted to, himself, a person who is an officer subject to Rule 16b-3 or a
member of the Board. Subject to the terms of the Plan and applicable law, and in
addition to other express powers and authorizations conferred on the Committee
by the Plan, the Committee shall have full power and authority to: (i) designate
Participants; (ii) determine the type or types of Awards to be granted to a
Participant; (iii) determine the number of Units to be covered by Awards; (iv)
determine the terms and conditions of any Award; (v) determine whether, to what
extent, and under what circumstances Awards may be settled, exercised, canceled,
or forfeited; (vi) interpret and administer the Plan and any instrument or
agreement relating to an Award made under the Plan; (vii) establish, amend,
suspend, or waive such rules and regulations and appoint such agents as it shall
deem appropriate for the proper administration of the Plan; and (viii) make any
other determination and take any other action that the Committee deems necessary
or desirable for the administration of the Plan. Unless otherwise expressly
provided in the Plan, all designations, determinations, interpretations, and
other decisions under or with respect to the Plan or any Award shall be within
the sole discretion of the Committee, may be made at any time and shall be
final, conclusive, and binding upon all Persons, including the Company, the
Partnership, any Affiliate, any Participant, and any beneficiary of any Award.

SECTION 4. UNITS.

     (a)   UNITS AVAILABLE. Subject to adjustment as provided in Section 4(c),
the number of Units with respect to which (i) Phantom Units may be granted under
the Plan is 200,000 and (ii) Options may be granted under the Plan is 300,000.
If any Option or Phantom Unit is forfeited or otherwise terminates or is
canceled without the delivery of Units, then the Units covered by such Award, to
the extent of such forfeiture, termination or cancellation, shall again be Units
with respect to which an Option or Phantom Unit may be granted, as the case may
be.

     (b)   SOURCES OF UNITS DELIVERABLE UNDER AWARDS. Any Units delivered
pursuant to an Award shall consist, in whole or in part, of Units acquired in
the open market, from any Affiliate, the Partnership or any other Person, or any
combination of the foregoing, as determined by the Committee in its discretion.

     (c)   ADJUSTMENTS. In the event that the Committee determines that any
distribution (whether in the form of cash, Units, other securities, or other
property), recapitalization, split, reverse split, reorganization, merger,
consolidation, split-up, spin-off, combination, repurchase, or exchange of Units
or other securities of the Partnership, issuance of warrants or other rights to
purchase Units or other securities of the Partnership, or other similar
transaction or event affects the Units such that an adjustment is determined by
the Committee to be appropriate in order to prevent dilution or enlargement of
the benefits or potential benefits intended to be made available under the Plan,
then the Committee shall, in such manner as it may deem equitable, adjust any or
all of (i) the number and

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type of Units (or other securities or property) with respect to which Awards may
be granted, (ii) the number and type of Units (or other securities or property)
subject to outstanding Awards, and (iii) the grant or exercise price with
respect to any Award or, if deemed appropriate, make provision for a cash
payment to the holder of an outstanding Award; provided, that the number of
Units subject to any Award shall always be a whole number.

SECTION 5. ELIGIBILITY.

     Any Employee who performs services for the benefit of the Partnership, as
determined by the Committee, or any Director shall be eligible to be designated
a Participant and receive an Award under the Plan.

SECTION 6. AWARDS.

     (a)   OPTIONS. The Committee shall have the authority to determine the
Employees and Directors to whom Options shall be granted, the number of Units to
be covered by each Option, the purchase price therefor, the Restricted Period
and the conditions and limitations applicable to the exercise of the Option,
including the following terms and conditions and such additional terms and
conditions, as the Committee shall determine, that are not inconsistent with the
provisions of the Plan.

           (i)   EXERCISE PRICE. The purchase price per Unit purchasable under
     an Option shall be determined by the Committee at the time the Option is
     granted and may be more or less than its Fair Market Value as of the date
     of grant.

           (ii)  TIME AND METHOD OF EXERCISE. The Committee shall determine the
     Restricted Period, i.e., the time or times at which an Option may be
     exercised in whole or in part, which may include, without limitation,
     accelerated vesting upon the achievement of specified performance goals,
     and the method or methods by which payment of the exercise price with
     respect thereto may be made or deemed to have been made, which may include,
     without limitation, cash, check acceptable to the Company, a
     "cashless-broker" exercise through procedures approved by the Company, a
     recourse note from the Participant in a form acceptable to the Company, or
     any combination thereof, having a Fair Market Value on the exercise date
     equal to the relevant exercise price.

           (iii) FORFEITURE. Except as otherwise provided in the terms of the
     Option grant, upon termination of a Participant's employment with the
     Company and its Affiliates or membership on the Board, whichever is
     applicable, for any reason during the applicable Restricted Period, all
     Options shall be forfeited by the Participant. The Committee may, in its
     discretion, waive in whole or in part such forfeiture with respect to a
     Participant's Options.

     (b)   PHANTOM UNITS. The Committee shall have the authority to determine\
the Employees and Directors to whom Phantom Units shall be granted, the number
of Phantom Units to be granted to each such Participant, the Restricted Period,
the conditions under which the Phantom Units may become vested or forfeited,
which may include, without limitation, the accelerated vesting upon the

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achievement of specified performance goals, and such other terms and conditions
as the Committee may establish with respect to such Awards, including whether
DERs are granted with respect to such Phantom Units.

           (i)   DERs. Each of the initial 55,000 Phantom Units granted under
     the Plan shall include a tandem DER grant. No other DERs may be granted
     under the Plan.

           (ii)  FORFEITURE. Except as otherwise provided in the terms of the
     Phantom Units grant, upon termination of a Participant's employment with
     the Company and its Affiliates or membership on the Board, whichever is
     applicable, for any reason during the applicable Restricted Period, all
     Phantom Units shall be forfeited by the Participant. The Committee may, in
     its discretion, waive in whole or in part such forfeiture with respect to a
     Participant's Phantom Units.

           (iii) LAPSE OF RESTRICTIONS. Upon or as soon as reasonably practical
     following the vesting of each Phantom Unit, the Participant shall be
     entitled to receive from the Company one Unit or cash equal to the Fair
     Market Value of a Unit, as determined by the Committee in its discretion.

     (c)   GENERAL.

           (i)   AWARDS MAY BE GRANTED SEPARATELY OR TOGETHER. Awards may, in
     the discretion of the Committee, be granted either alone or in addition to,
     in tandem with, or in substitution for any other Award granted under the
     Plan or any award granted under any other plan of the Company or any
     Affiliate. Awards granted in addition to or in tandem with other Awards or
     awards granted under any other plan of the Company or any Affiliate may be
     granted either at the same time as or at a different time from the grant of
     such other Awards or awards.

           (ii)  LIMITS ON TRANSFER OF AWARDS.

                 (A)  Except as provided in (C) below, each Option shall be
           exercisable only by the Participant during the Participant's
           lifetime, or by the person to whom the Participant's rights shall
           pass by will or the laws of descent and distribution.

                 (B)  Except as provided in (C) below, no Award and no right
           under any such Award may be assigned, alienated, pledged, attached,
           sold or otherwise transferred or encumbered by a Participant and any
           such purported assignment, alienation, pledge, attachment, sale,
           transfer or encumbrance shall be void and unenforceable against the
           Company or any Affiliate.

                 (C)  To the extent specifically provided by the Committee with
           respect to an Option grant, an Option may be transferred by a
           Participant without consideration to immediate family members or
           related family trusts, limited partnerships or similar entities or on
           such terms and conditions as the Committee may from time to time
           establish. In addition, Awards may be transferred by will and the
           laws of descent and distribution.

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           (iii) TERM OF AWARDS. The term of each Award shall be for such period
     as may be determined by the Committee.

           (iv)  UNIT CERTIFICATES. All certificates for Units or other
     securities of the Partnership delivered under the Plan pursuant to any
     Award or the exercise thereof shall be subject to such stop transfer orders
     and other restrictions as the Committee may deem advisable under the Plan
     or the rules, regulations, and other requirements of the SEC, any stock
     exchange upon which such Units or other securities are then listed, and any
     applicable federal or state laws, and the Committee may cause a legend or
     legends to be put on any such certificates to make appropriate reference to
     such restrictions.

           (v)   CONSIDERATION FOR GRANTS. Awards may be granted for such
     consideration, including services, as the Committee determines.

           (vi)  DELIVERY OF UNITS OR OTHER SECURITIES AND PAYMENT BY
     PARTICIPANT OF CONSIDERATION. Notwithstanding anything in the Plan or any
     grant agreement to the contrary, delivery of Units pursuant to the exercise
     or vesting of an Award may be deferred for any period during which, in the
     good faith determination of the Committee, the Company is not reasonably
     able to obtain Units to deliver pursuant to such Award without violating
     the rules or regulations of any applicable law or securities exchange. No
     Units or other securities shall be delivered pursuant to any Award until
     payment in full of any amount required to be paid pursuant to the Plan or
     the applicable Award grant agreement (including, without limitation, any
     exercise price or tax withholding) is received by the Company. Such payment
     may be made by such method or methods and in such form or forms as the
     Committee shall determine, including, without limitation, cash, other
     Awards, withholding of Units, cashless-broker exercises with simultaneous
     sale, or any combination thereof; provided that the combined value, as
     determined by the Committee, of all cash and cash equivalents and the Fair
     Market Value of any such Units so tendered to the Company, as of the date
     of such tender, is at least equal to the full amount required to be paid to
     the Company pursuant to the Plan or the applicable Award agreement.

           (vii) CHANGE IN CONTROL. Upon a Change in Control or such period
     prior thereto as may be established by the Committee, all Awards shall
     automatically vest and become payable or exercisable, as the case may be,
     in full. In this regard, all Restricted Periods shall terminate and all
     performance criteria, if any, shall be deemed to have been achieved at the
     maximum level. To the extent an Option is not exercised upon a Change in
     Control, the Committee may, in its discretion, cancel such Award without
     payment or provide for a replacement grant with respect to such property
     and on such terms as it deems appropriate.

SECTION 7. AMENDMENT AND TERMINATION.

     Except to the extent prohibited by applicable law:

     (a)   AMENDMENTS TO THE PLAN. Except as required by the rules of the
principal securities exchange on which the Units are traded and subject to
Section 7(b) below, the Board or the Committee may amend, alter, suspend,
discontinue, or terminate the Plan in any manner, including

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increasing the number of Units available for Awards under the Plan, without the
consent of any partner, Participant, other holder or beneficiary of an Award, or
other Person.

     (b)   AMENDMENTS TO AWARDS. Subject to Section 7(a), the Committee may
waive any conditions or rights under, amend any terms of, or alter any Award
theretofore granted, provided no change, other than pursuant to Section 7(c), in
any Award shall materially reduce the benefit to a Participant without the
consent of such Participant.

     (c)   ADJUSTMENT OF AWARDS UPON THE OCCURRENCE OF CERTAIN UNUSUAL OR
NONRECURRING EVENTS. The Committee is hereby authorized to make adjustments in
the terms and conditions of, and the criteria included in, Awards in recognition
of unusual or nonrecurring events (including, without limitation, the events
described in Section 4(c) of the Plan) affecting the Partnership or the
financial statements of the Partnership, or of changes in applicable laws,
regulations, or accounting principles, whenever the Committee determines that
such adjustments are appropriate in order to prevent dilution or enlargement of
the benefits or potential benefits intended to be made available under the Plan.

SECTION 8. GENERAL PROVISIONS.

     (a)   NO RIGHTS TO AWARD. No Person shall have any claim to be granted any
Award under the Plan, and there is no obligation for uniformity of treatment of
Participants. The terms and conditions of Awards need not be the same with
respect to each recipient.

     (b)   WITHHOLDING. The Company or any Affiliate is authorized to withhold
from any Award, from any payment due or transfer made under any Award or from
any compensation or other amount owing to a Participant the amount (in cash,
Units, other securities, Units that would otherwise be issued pursuant to such
Award or other property) of any applicable taxes payable in respect of the grant
of an Award, its exercise, the lapse of restrictions thereon, or any payment or
transfer under an Award or under the Plan and to take such other action as may
be necessary in the opinion of the Company or Affiliate to satisfy its
withholding obligations for the payment of such taxes.

     (c)   NO RIGHT TO EMPLOYMENT. The grant of an Award shall not be construed
as giving a Participant the right to be retained in the employ of the Company or
any Affiliate or to remain on the Board, as applicable. Further, the Company or
an Affiliate may at any time dismiss a Participant from employment, free from
any liability or any claim under the Plan, unless otherwise expressly provided
in the Plan or in any Award agreement.

     (d)   GOVERNING LAW. The validity, construction, and effect of the Plan and
any rules and regulations relating to the Plan shall be determined in accordance
with the laws of the State of Delaware law without regard to its conflict of
laws principles.

     (e)   SEVERABILITY. If any provision of the Plan or any award is or becomes
or is deemed to be invalid, illegal, or unenforceable in any jurisdiction or as
to any Person or Award, or would disqualify the Plan or any award under any law
deemed applicable by the Committee, such provision shall be construed or deemed
amended to conform to the applicable laws, or if it cannot be construed

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or deemed amended without, in the determination of the Committee, materially
altering the intent of the Plan or the Award, such provision shall be stricken
as to such jurisdiction, person or award and the remainder of the Plan and any
such Award shall remain in full force and effect.

     (f)   OTHER LAWS. The Committee may refuse to issue or transfer any Units
or other consideration under an Award if, in its sole discretion, it determines
that the issuance or transfer or such Units or such other consideration might
violate any applicable law or regulation, the rules of the principal securities
exchange on which the Units are then traded, or entitle the Partnership or an
Affiliate to recover the same under Section 16(b) of the Exchange Act, and any
payment tendered to the Company by a Participant, other holder or beneficiary in
connection with the exercise of such Award shall be promptly refunded to the
relevant Participant, holder or beneficiary.

     (g)   NO TRUST OR FUND CREATED. Neither the Plan nor any Award shall
create or be construed to create a trust or separate fund of any kind or a
fiduciary relationship between the Company or any participating Affiliate and a
Participant or any other Person. To the extent that any Person acquires a right
to receive payments from the Company or any participating Affiliate pursuant to
an award, such right shall be no greater than the right of any general unsecured
creditor of the Company or any participating Affiliate.

     (h)   NO FRACTIONAL UNITS. No fractional Units shall be issued or delivered
pursuant to the Plan or any Award, and the Committee shall determine whether
cash, other securities, or other property shall be paid or transferred in lieu
of any fractional Units or whether such fractional Units or any rights thereto
shall be canceled, terminated, or otherwise eliminated.

     (i)   HEADINGS. Headings are given to the Sections and subsections of the
Plan solely as a convenience to facilitate reference. Such headings shall not be
deemed in any way material or relevant to the construction or interpretation of
the Plan or any provision thereof.

     (j)   FACILITY PAYMENT. Any amounts payable hereunder to any person under
legal disability or who, in the judgment of the Committee, is unable to properly
manage his financial affairs, may be paid to the legal representative of such
person, or may be applied for the benefit of such person in any manner which the
Committee may select, and the Company shall be relieved of any further liability
for payment of such amounts.

     (k)   GENDER AND NUMBER. Words in the masculine gender shall include the
feminine gender, the plural shall include the singular and the singular shall
include the plural.

SECTION 9. TERM OF THE PLAN.

     The Plan shall be effective on the date of its approval by the Board and
shall continue until the date terminated by the Board or Units are no longer
available for the payment of Awards under the Plan, whichever occurs first.
However, unless otherwise expressly provided in the Plan or in an applicable
Award Agreement, any Award granted prior to such termination, and the authority
of the Board or the Committee to amend, alter, adjust, suspend, discontinue, or
terminate any such Award or to waive any conditions or rights under such Award,
shall extend beyond such termination date.

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