UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-K/A

Amendment No. 1

(Mark One)

x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

for the fiscal year ended December 31, 2003

or

¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

for the transition period from                      to                     .

Commission File No. 000-31953

CATALYTICA ENERGY SYSTEMS, INC.

(Exact name of Registrant as specified in its charter)

Delaware	77-0410420
(State or other jurisdiction of incorporation or organization)	(IRS Employer Identification Number)

1388 North Tech Boulevard

Gilbert, Arizona 85233

(Address of principal executive offices)

(480) 556-5555

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

None

Securities registered pursuant to Section 12(g) of the Act:

Common Stock, $0.001 par value

(Title of Class)

Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes  x    No  ¨

Indicate by check mark whether the Registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  x

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.    x

As of March 19, 2004, there were outstanding 17,827,312 shares of the Registrant’s common stock, par value $0.001, which is the only class of common stock of the Registrant registered under Section 12(g) of the Securities Act of 1933.

As of June 30, 2003, the aggregate market value of the shares of common stock held by non-affiliates of the Registrant (based on the last sale price for the common stock on The NASDAQ Stock Market on such date) was $25,868,665. For purposes of this computation, all officers, directors and 5% beneficial owners of the Registrant’s common stock are deemed to be affiliates. Such determination should not be deemed to be an admission or representation that such officers, directors or 5% beneficial owners are, in fact, affiliates of the Registrant.

Documents Incorporated by Reference

None in this Form 10-K/A.

Explanatory Note

Catalytica Energy Systems, Inc. (the “Company”) is filing this Form 10-K/A to the Form 10-K for the fiscal year ended December 31, 2003, as filed with the Securities and Exchange Commission on March 30, 2004, solely to modify and replace the previously filed certifications contained in Exhibits 31.1, 31.2, 32.1 and 32.2, which inadvertently were based on former versions of these certifications, effective as of the date of the original certifications.

2

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities and Exchange Act of 1934, the Registrant has duly caused this Report to be signed on its behalf by the undersigned, thereunto duly authorized.

	CATALYTICA ENERGY SYSTEMS, INC. (Registrant)
Dated: May 14, 2004	By:	/s/    Michael J. Murry
		Michael J. Murry President and Chief Executive Officer

3

EXHIBITS INDEX

Exhibit	Description
31.1	Certification of Chief Executive Officer pursuant to Rule 13a-14(a) / 15d-14(a) of the Securities Exchange Act of 1934, as amended
31.2	Certification of Chief Financial Officer pursuant to Rule 13a-14(a) / 15d-14(a) of the Securities Exchange Act of 1934, as amended
32.1	Certification of Chief Executive Officer pursuant to 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.
32.2	Certification of Chief Financial Officer pursuant to 18 U.S.C. 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002.

4