ST. LOUIS (September 22, 2006) – Arch Coal, Inc. (NYSE:ACI) today announced that its Skyline mine achieved the nation's best underground coal mine safety record in 2005, according to the Mine Safety and Health Administration (MSHA).

The prestigious Sentinels of Safety award was presented to Skyline at a banquet on Sept. 21 in Washington, D.C.

The Skyline mine is located near Scofield, Utah, and utilizes both longwall and continuous mining systems. Skyline employees worked more than 28 months and 500,000 employee-hours without a single reportable or lost-time injury.

"This is a great tribute to the dedicated men and women at Skyline who have embraced safety as a core value and guiding principle," said Arch Coal's Chairman and Chief Executive Officer Steven F. Leer. "Constant vigilance and continuous improvement in mine safety are absolutely necessary – and Arch Coal's Skyline employees are leading by example."

The Sentinels of Safety awards program is cosponsored by MSHA and the National Mining Association. The program has been presented annually since 1925 to recognize extremely noteworthy accomplishments in the area of mine health and safety.

The Sentinels of Safety awards are presented to U.S. mine operations that have worked the most employee-hours without experiencing a lost-time injury. Visit MSHA's Web site (www.msha.gov) for a list of the award categories and recipients.

Arch Coal is the nation's second largest coal producer. The company's core business is providing U.S. power generators with clean-burning, low-sulfur coal for electric generation. Through its national network of mines, Arch supplies the fuel for approximately 6 percent of the electricity generated in the United States. Arch's subsidiaries achieved an overall 2005 safety record that was the best in the history of the company. For a complete list of Arch's national and state honors, visit www.archcoal.com/aboutus/awards.asp.