Atlas Energy Resources, LLC Increases Public Offering To 1.8 Million Common Units

Business Wire, May 16, 2008

PITTSBURGH -- Atlas Energy Resources, LLC (NYSE: ATN) ("Atlas Energy") announces today that it has increased its previously announced public offering of 1.6 million common units representing Class B limited liability company interests to 1.8 million common units. UBS Investment Bank and Wachovia Securities acted as joint book-running managers and underwriters of this offering. The option to purchase additional common units granted to the underwriters has also been increased to 270,000 common units.

Atlas Energy intends to use the net proceeds of the offering to repay a portion of its outstanding balance under its revolving credit facility. The increased borrowing capacity will be used to fund additional acreage acquisitions and accelerated development of the Marcellus Shale as well as further development of its other drilling programs and lease acquisition activities.

This press release does not constitute an offer to sell or a solicitation of an offer to buy any securities. The offer is being made only through the prospectus supplement and accompanying base prospectus, which is part of a registration statement that became effective on March 13, 2008.

When available, a copy of the prospectus supplement and accompanying base prospectus relating to the public offering may be obtained from the underwriters as follows:

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UBS Investment Bank
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Attention: Prospectus Department
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299 Park Avenue
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New York, NY 10171
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Toll free: 888-827-7275
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Wachovia Securities
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Equity Syndicate Department
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375 Park Avenue
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New York, NY 10152
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Email: equity.syndicate@wachovia.com

Atlas Energy Resources, LLC develops and produces domestic natural gas and to a lesser extent, oil. Atlas Energy is one of the largest independent energy producers in the Appalachian Basin and northern Michigan. Atlas Energy sponsors and manages tax-advantaged investment partnerships, in which it co-invests, to finance the exploration and development of its acreage in the Appalachian Basin. Atlas Energy is active principally in Pennsylvania, Michigan and Tennessee. For more information, visit Atlas Energy's website at www.atlasenergyresources.com or contact Investor Relations at bbegley@atlasamerica.com.

Certain matters discussed within this press release are forward-looking statements. Although Atlas Energy Resources, LLC believes the expectations reflected in such forward-looking statements are based on reasonable assumptions, it can give no assurance that its expectations will be attained. Factors that could cause actual results to differ materially from expectations include financial performance, regulatory changes, changes in local or national economic conditions and other risks detailed from time to time in Atlas Energy's reports filed with the SEC, including quarterly reports on Form 10-Q, reports on Form 8-K and annual reports on Form 10-K.