Expand Energy (EXE) 10-Q 2009 Q2 Quarterly report

Exhibit 32.1

CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,

AS ADOPTED PURSUANT TO SECTION 906

OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Chesapeake Energy Corporation (the “Company”) on Form 10-Q for the Period ended June 30, 2009 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I Aubrey K. McClendon, Chairman and Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C.§ 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that:

1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange act of 1934; and

2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

/s/ AUBREY K. MCCLENDON

Aubrey K. McClendon

Chairman of the Board and Chief Executive Officer

Date: August 10, 2009