UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

         DIVISION OF
CORPORATION FINANCE
Mail Stop 7010
      May 19, 2006

via U.S. mail

Mr. Andrew L. Schroeder
Vice President, Finance and Treasurer
MarkWest Energy Partners, L.P.
155 Inverness Drive West, Suite 200
Englewood, Colorado 80112-5000

      Re:	MarkWest Energy Partners, L.P.
      	Form S-1
      	Filed April 20, 2006
      	File No. 333-133439

      	Form S-1
      	Filed April 25, 2006
      File No. 333-133534

      Form 10-K for the fiscal year ended December 31, 2005
      Filed March 16, 2006, as amended March 31, 2006
      File No. 1-31239

      Form 10-Q/A for the quarter ended March 31, 2006
      Filed May 4, 2006

Dear Mr. Schroeder:

      We have limited our review of your filings to those issues
we
have addressed in our comments.  Where indicated, we think you
should
revise your documents in response to these comments.  If you
disagree, we will consider your explanation as to why our comment
is
inapplicable or a revision is unnecessary.  Please be as detailed
as
necessary in your explanation.  In some of our comments, we may
ask
you to provide us with information so we may better understand
your
disclosure.  After reviewing this information, we may raise
additional comments.

      Please understand that the purpose of our review process is
to
assist you in your compliance with the applicable disclosure
requirements and to enhance the overall disclosure in your
filings.
We look forward to working with you in these respects.  We
welcome any questions you may have about our comments or any other
aspect of our review.  Feel free to call us at the telephone
numbers
listed at the end of this letter.

General

1.	You will expedite the review process if you address each
portion
of every numbered comment that appears in this letter.  Provide
complete responses and, where disclosure has changed, indicate
precisely where in the marked version of the amendment we will
find
your responsive changes.  Similarly, to minimize the likelihood
that
we will reissue comments, please make corresponding changes where
applicable throughout your documents.  For example, we might
comment
on one section or example in one document, but our silence on
similar
or related disclosure elsewhere in the same document or in a
different document does not relieve you of the need to make
similar
revisions elsewhere as appropriate.

2.	The safe harbor for forward-looking statements set forth in
Section 27A of the Securities Act does not apply to statements
made
in connection with an offering by or relating to the operations of
a
partnership.  Revise all your filings to eliminate any suggestion
to
the contrary.  See Section 27A(b)(2)(E).

3.	Disclose clearly and with specificity in each registration
statement the size and details of the other offering so that
potential investors are aware of both.  Make parallel changes
throughout the prospectus as appropriate, for example where you
discuss potential dilution or the increased number of freely
tradable
shares.  Also ensure that any other material ramifications of the
concurrent offerings are made clear, including the impact of the
underwritten transaction on the potential number of new shares in
the
market prior to completion of the other transaction.  We may have
additional comments.

4.	With regard to the underwritten offering, provide all the
disclosure Item 507 of Regulation S-K requires.

Form S-1 filed April 20, 2006

Risk Factors

"We have found material weaknesses in our internal controls...,"
page
8

5.	Expand the caption and text to make clear that material
weaknesses also existed at December 31, 2003.  Also make clear the
potential risks to stockholders that could result from the
material
weaknesses going forward.


6. 	Delete from the Risk Factors section any language that serves
to
mitigate or qualify the risk that you are highlighting.  Examples
of
this are: "while we have undertaken numerous steps in an effort to
remediate our material weaknesses" and the first two sentences of
the
penultimate paragraph.

7.	Provide elsewhere in the prospectus enhanced detail on all
steps
that you have taken, are taking and plan to take to rectify this
situation, rather than including this information in the Risk
Factors
section.

 Selling Unitholders, page 39

8.	Revise as necessary to identify the natural person with power
to
vote or to dispose of the securities offered for resale by the
entity
listed as a selling unitholder.  Also provide clarifying
disclosure
as necessary to explain the relationship among the various
"Tortoise"
entities listed in the tables and footnotes at pages 36 and 39.

Where You Can Find More Information, page 86

9.	If you incorporate by reference, include all Exchange Act
reports filed since the beginning of your current fiscal year.

Form S-1 filed April 25, 2006

Management`s Discussion and Analysis of Financial Condition and
Results of Operations

Overview -- Material Weaknesses Reported for the Years Ended
December
31, 2005 and 2004, page 62

10.	Expand the caption to refer also to 2003, and disclose the
material weaknesses identified for all three periods.  For each
identified material weakness, disclose when it was identified, who
identified the material weakness, the causes for the material
weakness, the steps you have taken to rectify the situation, and
where applicable, why the material weakness persists or continued
during a prolonged period of time.  This comment also applies to
related disclosure in your other filings, including without
limitation your controls and procedures disclosure in your most
recent Form 10-K.  We may have additional comments.

11.	Where there are limitations on the scope of your analysis,
for
example regarding the Javelina entities, revise to make this
clear.





Changes in Internal Control Over Financial Reporting, page 64

12.	Explain with greater specificity when you made each of the
changes you identify, and provide all the disclosure that Item
308(c)
of Regulation S-K requires.  Make parallel changes to your other
filings, including your Form 10-K and most recent Form 10-Q, as
appropriate.

Form 10-K for the fiscal year ended December 31, 2005, as amended

13.	As appropriate, amend within 10 business days your Form 10-K
and
Form 10-Q in response to all applicable comments, including the
following comment.

Exhibits 31.1 and 31.2

14.	Please file revised exhibits that comply with the
requirements
of Item 601(b)(32) of Regulation S-K.

Closing Comments

      As appropriate, please amend your registration statements in
response to these comments.  You may wish to provide us with
marked
copies of the amendments to expedite our review.  Please furnish a
cover letter with your amendments that keys your responses to our
comments and provides any requested information.  Detailed cover
letters greatly facilitate our review.  Please understand that we
may
have additional comments after reviewing your amendments and
responses to our comments.

      We urge all persons who are responsible for the accuracy and
adequacy of the disclosure in the filing to be certain that the
filing includes all information required under the Securities Act
of
1933 and that they have provided all information investors require
for an informed investment decision.  Since the company and its
management are in possession of all facts relating to a company`s
disclosure, they are responsible for the accuracy and adequacy of
the
disclosures they have made.

      Notwithstanding our comments, in the event the company
requests
acceleration of the effective date of the pending registration
statements, it should furnish a letter, at the time of such
request,
acknowledging that:

?	should the Commission or the staff, acting pursuant to
delegated
authority, declare the filing effective, it does not foreclose the
Commission from taking any action with respect to the filing;

?	the action of the Commission or the staff, acting pursuant to
delegated authority, in declaring the filing effective, does not
relieve the company from its full responsibility for the adequacy
and
accuracy of the disclosure in the filing; and

?	the company may not assert staff comments and the declaration
of
effectiveness as a defense in any proceeding initiated by the
Commission or any person under the federal securities laws of the
United States.

      In addition, please be advised that the Division of
Enforcement
has access to all information you provide to the staff of the
Division of Corporation Finance in connection with our review of
your
filings or in response to our comments on your filing.

      We will consider a written request for acceleration of the
effective date of the registration statements as confirmation of
the
fact that those requesting acceleration are aware of their
respective
responsibilities under the Securities Act of 1933 and the
Securities
Exchange Act of 1934 as they relate to the proposed public
offering
of the securities specified in the above registration statements.
We
will act on the request and, pursuant to delegated authority,
grant
acceleration of the effective date.

      We direct your attention to Rules 460 and 461 regarding
requesting acceleration of a registration statements.  Please
allow
adequate time after the filing of any amendment for further review
before submitting a request for acceleration.  Please provide this
request at least two business days in advance of the requested
effective date.

      Please contact Donna Levy at (202) 551-3292, or in her
absence,
Timothy Levenberg, Special Counsel, at (202) 551-3707, with any
questions.

      Sincerely,



      H. Roger Schwall
      Assistant Director


cc:	David P. Oelman, Esq.
      D. Levy
      T. Levenberg


Mr. Andrew L. Schroeder
MarkWest Energy Partners, L.P.
May 19, 2006
page 5