<DOCUMENT>
<TYPE>EX-21
<SEQUENCE>4
<FILENAME>a2043140zex-21.txt
<DESCRIPTION>EXHIBIT 21
<TEXT>

<PAGE>

                                   EXHIBIT 21

                           MARKWEST HYDROCARBON, INC.
                              LIST OF SUBSIDIARIES


<TABLE>
<CAPTION>
NAME OF SUBSIDIARY                           TYPE OF ENTITY                          RELATION
------------------                           --------------                          --------
<S>                                          <C>                                     <C>
MarkWest Michigan, Inc.                      Colorado Corporation                    Wholly-owned subsidiary

West Shore Processing Company, LLC           Michigan Limited Liability Company      Wholly-owned subsidiary

Basin Pipeline, LLC                          Michigan Limited Liability Company      Wholly-owned subsidiary

MarkWest Resources, Inc.                     Colorado Corporation                    Wholly-owned subsidiary

Matrex, LLC                                  Michigan Limited Liability Company      Wholly-owned subsidiary

</TABLE>

</TEXT>
</DOCUMENT>