MarkWest Energy Partners Announces Exercise of Option to Purchase Additional Units

DENVER--(Business Wire)--
MarkWest Energy Partners, L.P. (NYSE:MWE) announced today that the
underwriters of its common unit offering exercised in full their
option to purchase an additional 750,000 common units at $31.15. The
option was granted in connection with the Partnership's offering of
5,000,000 common units, which priced on April 8, 2008. MarkWest
expects net proceeds from the offering, including the exercise of the
over-allotment option, to be approximately $172 million.

Lehman Brothers and Morgan Stanley acted as joint book-running
managers for the offering. RBC Capital Markets and Wachovia Securities
acted as senior co-managers, and Deutsche Bank Securities and JPMorgan
acted as co-managers. A copy of the final prospectus supplement and
related base prospectus associated with this offering may be obtained
from the underwriters by contacting Lehman Brothers c/o Broadridge
Integrated Distribution Services, 1155 Long Island Avenue, Edgewood,
NY 11717, qiana.smith@broadridge.com, fax (631) 254-7140; or Morgan
Stanley, Attn: Prospectus Dept., 180 Varick Street, 2nd Floor, New
York, New York 10014, prospectus@morganstanley.com, phone (866)
718-1649.

This press release shall not constitute an offer to sell or the
solicitation of an offer to buy nor shall there be any sale of these
securities in any state in which such offer, solicitation, or sale
would be unlawful prior to registration or qualification under the
securities laws of such state.

MarkWest Energy Partners, L.P. (NYSE:MWE) is a publicly traded
master limited partnership with a solid core of midstream assets and a
growing core of gas transmission assets. It is one of the largest
processors of natural gas in the Northeast and is the largest gas
gatherer of natural gas in the prolific Carthage field in east Texas.
It also has a growing number of other gas gathering and intrastate gas
transmission assets in the Southwest, primarily in Texas and Oklahoma.

This press release includes "forward-looking statements." All
statements other than statements of historical facts included or
incorporated herein may constitute forward-looking statements. Actual
results could vary significantly from those expressed or implied in
such statements and are subject to a number of risks and
uncertainties. Although we believe that the expectations reflected in
the forward-looking statements are reasonable, we can give no
assurance that such expectations will prove to be correct. The
forward-looking statements involve risks and uncertainties that affect
our operations, financial performance and other factors as discussed
in our filings with the Securities and Exchange Commission. Among the
factors that could cause results to differ materially are those risks
discussed in our Form 10-K for the year ended December 31, 2007, as
filed with the SEC. You are urged to carefully review and consider the
cautionary statements and other disclosures made in those filings,
specifically those under the heading "Risk Factors." We do not
undertake any duty to update any forward-looking statement except as
required by law.

MarkWest Energy Partners, L.P.
Frank Semple, 866-858-0482
President and CEO
or
Nancy Buese, 866-858-0482
Senior VP and CFO
or
Andy Schroeder, 866-858-0482
VP of Finance/Treasurer
Fax: 303-925-8709
investorrelations@markwest.com
www.markwest.com

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