**Exhibit 31.1**

 

**CERTIFICATION**

 

I,Frank M. Semple, certify that:

 

1. Ihave reviewed this annual report on Form 10-K/A of MarkWest EnergyPartners, L.P.

 

2.Based on my knowledge, this report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report.

 

3.Based on my knowledge, the financial statements, and other financialinformation included in this report, fairly present in all material respectsthe financial condition, results of operations and cash flows of the registrantas of, and for, the periods presented in this report.

 

4. The registrant’s othercertifying officers and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) and internal control over financial reporting (as defined inExchange Act Rules 13a-15(f) and 15d-15(f) for the registrantand have:

 

a)              Designed such disclosure controls and procedures, orcaused such disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to the registrant,including its consolidated subsidiaries, is made known to us by others withinthose entities, particularly during the period in which this report is beingprepared;

 

b)             Designed such internal control over financialreporting, or caused such internal control over financial reporting to bedesigned under our supervision, to provide reasonable assurance regarding thereliability of financial reporting and the preparation of financial statementsfor external purposes in accordance with generally accepted accounting principles;

 

c)              Evaluated the effectiveness of the registrant’sdisclosure controls and procedures****andpresented in this report our conclusions about the effectiveness of thedisclosure controls and procedures, as of the end of the period covered by thisreport based on such evaluation**;**and

 

d)             Disclosed in this report any change in the registrant’sinternal control over financial reporting that occurred during the registrant’smost recent fiscal quarter (the registrant’s fourth fiscal quarter in the caseof an annual report) that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting;and

 

5. The registrant’s othercertifying officers and I have disclosed, based on our most recent evaluationof internal control over financial reporting, to the registrant’s auditors andthe audit committee of registrant’s board of directors (or persons performingthe equivalent function):

 

a)              All significant deficiencies and material weaknessesin the design or operation of internal control over financial reporting whichare reasonably likely to adversely affect the registrant’s ability to record,process, summarize and report financial information; and

 

b)             Any fraud, whether or not material, that involvesmanagement or other employees who have a significant role in the registrant’sinternal control over financial reporting.

 
| Date: May 7, 2008 | By:    | /S/ FRANK M. SEMPLE |
|------------------------|--------|---------------------|
|                   |   |                |   | Frank M. Semple |
|                   |   |                |   | President and Chief Executive Officer   (Principal Executive Officer) |

 

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