MWP Markwest Hydrocarbon,

DENVER, Sept. 6 /PRNewswire-FirstCall/ -- MarkWest Hydrocarbon, Inc. (AMEX:MWP) today announced the upcoming retirement of Jim Ivey, Chief Financial Officer. Mr. Ivey will continue as CFO until October 1, 2006, the date set for his retirement. He cited the desire to pursue other family and personal interests in reaching his decision to retire. "Jim has been instrumental in developing MarkWest's financial strategy and executing our business plan," said Frank Semple, President and CEO. "Jim's experience will be missed; however, I am pleased to also announce that Nancy K. Masten has been named as the acting Chief Financial Officer while the Board of Directors considers all options for filling this very critical position. Nancy is our current Chief Accounting Officer and her previous experience as the CFO for EAS, Inc. (a subsidiary of the Ross Products Division of Abbott Laboratories), Vice President for TransMontaigne, Inc. and as a Partner with Ernst & Young LLP will allow her to provide excellent leadership as the acting Chief Financial Officer." MarkWest Hydrocarbon, Inc. (AMEX:MWP) controls and operates MarkWest Energy Partners, L.P. (AMEX:MWE), a publicly-traded limited partnership engaged in the gathering, processing and transmission of natural gas; the transportation, fractionation and storage of natural gas liquids; and the gathering and transportation of crude oil. We also market natural gas and NGLs. This press release includes "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. All statements other than statements of historical facts included or incorporated herein may constitute forward-looking statements. 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 ("SEC"). 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, 2005, and our Forms 10-Q for 2006, as filed with the SEC. DATASOURCE: MarkWest Hydrocarbon, Inc. CONTACT: Frank Semple, President & CEO, or Jim Ivey, CFO, or Andy Schroeder, VP and Treasurer, all of MarkWest Hydrocarbon, Inc., +1-866-858-0482, or fax, +1-303-290-8769, Web site: http://www.markwest.com/

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