QuickLinks -- Click here to rapidly navigate through this document

EXHIBIT 11

MARKWEST HYDROCARBON, INC.
COMPUTATION OF EARNINGS PER COMMON SHARE
(000s, except per share data)

	For the Quarter Ended June 30, 2002			For the Year Ended June 30, 2002
Net income (loss)	$	(2,075	)	$	(1,898	)
Weighted average number of outstanding shares of common stock		8,517			8,514
Basic earnings (loss) per share	$	(0.24	)	$	(0.22	)
Net income (loss)	$	(2,075	)	$	(1,898	)
Weighted average number of outstanding shares of common stock		8,517			8,514
Dilutive stock options		30			22
Earnings (loss) per share assuming dilution	$	(0.24	)	$	(0.22	)

QuickLinks

EXHIBIT 11