UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 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, 2011

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 number: 001-32953

ATLAS ENERGY, L.P.

(Exact name of registrant as specified in its charter)

Delaware	43-2094238
(State or other jurisdiction or incorporation or organization)	(I.R.S. Employer Identification No.)
Park Place Corporate Center One 1000 Commerce Drive, 4th Floor Pittsburgh, PA	15275
(Address of principal executive offices)	Zip code

Registrant’s telephone number, including area code: 412-489-0006

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

Title of each class	Name of each exchange on which registered
Common Units representing Limited Partnership Interests	New York Stock Exchange

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

None

Title of class

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    Yes  x    No  ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.    Yes  ¨    No  x

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 has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  x    No  ¨

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.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See definitions of “large accelerated filer”, “accelerated filer” and “small reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer	x	Accelerated filer	¨
Non-accelerated filer	¨	Smaller reporting company	¨

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  x

The aggregate market value of the voting common stock held by non-affiliates of the registrant, based on the closing price of such stock on the last business day of the registrant’s most recently completed second quarter, June 30, 2011, was approximately $1.1 billion.

The number of outstanding shares of the registrant’s common stock on February 22, 2012 was 51,297,814 shares.

DOCUMENTS INCORPORATED BY REFERENCE: None

Explanatory Note

The purpose of this Amendment No. 1 to our Annual Report on Form 10-K for the year ended December 31, 2011, as filed with the Securities and Exchange Commission on February 28, 2012, is to furnish Exhibit 101 to the Form 10-K, which provides certain items from our Form 10-K formatted in Extensible Business Reporting Language (“XBRL”).

No other changes have been made to the Form 10-K other than the furnishing of the exhibit described above. The Amendment No. 1 does not reflect subsequent events occurring after the original date of the Form 10-K or modify or update in any way disclosures made in the Form 10-K.

Exhibit 101 provides the following items formatted in XBRL: (i) Consolidated Combined Balance Sheets at December 31, 2011 and 2010; (ii) Consolidated Combined Statements of Operations for the fiscal years ended December 31, 2011, 2010 and 2009; (iii) Consolidated Combined Statements of Comprehensive Income (Loss) for the fiscal years ended December 31, 2011, 2010 and 2009; (iv) Consolidated Combined Statements of Partners’ Capital for the fiscal years ended December 31, 2011, 2010 and 2009; (v) Consolidated Combined Statements of Cash Flows for the fiscal years ended December 31, 2011, 2010 and 2009; and (vi) Notes to Consolidated Combined Financial Statements.

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EXHIBITS

Exhibit No.	Exhibits Description
101.INS	XBRL Instance Document
101.SCH	XBRL Schema Document
101.CAL	XBRL Calculation Linkbase Document
101.LAB	XBRL Label Linkbase Document
101.PRE	XBRL Presentation Linkbase Document
101.DEF	XBRL Definition Linkbase Document

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SIGNATURES

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

	ATLAS ENERGY, L.P.
	By:	Atlas Energy GP, LLC, its General Partner
Date: March 28, 2012	By:	/s/ SEAN P. MCGRATH
		Sean P. McGrath Chief Financial Officer

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