ST. LOUIS (October 18, 2004) - Arch Coal, Inc. (NYSE: ACI) announced today that it will offer publicly 6,250,000 shares of its Common Stock, $.01 par value per share. The company also will grant the underwriters an over-allotment option to purchase up to an additional 937,500 shares. The common stock will be issued under Arch Coal's universal shelf registration statement. Citigroup Global Markets Inc. and Morgan Stanley & Co. Incorporated are serving as joint book-running managers for the offering.

The Company intends to use the net proceeds of the offering to repay borrowings under its $350 million revolving credit facility incurred to finance its acquisition of Triton Coal Company, LLC and the first annual payment of $122.2 million under the Little Thunder federal coal lease, and for general corporate purposes, including the development of Mountain Laurel.

Copies of the prospectus relating to the public offering may be obtained from Citigroup Global Markets Inc., Brooklyn Army Terminal, 140 58th St., Brooklyn, New York, NY 11220 or from Morgan Stanley & Co. Incorporated, Prospectus Department, 1585 Broadway, New York, NY 10036.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy, nor shall there be any sales of these securities in any state or jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

Arch Coal is the nation's second largest coal producer with subsidiary operations in West Virginia, Kentucky, Virginia, Wyoming, Colorado and Utah. Through these operations, Arch Coal provides the fuel for approximately 7% of the electricity generated in the United States.