8-K

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 or 15(d) of the
Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 16, 2005 (December 16, 2005)

Arch Coal, Inc.

(Exact name of registrant as specified in its charter)

Delaware	1-13105	43-0921172
(State or other jurisdiction of incorporation)	(Commission File Number)	(I.R.S. Employer Identification No.)

CityPlace One, Suite 300, St. Louis, Missouri 63141

(Address of principal executive offices) (Zip code)

Registrant’s telephone number, including area code: (314) 994-2700

     Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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Exhibit Index begins on page 5.

Item 7.01 Regulation FD.

     In connection with Arch Coal, Inc.’s previously announced offer to pay a premium to holders of any and all of its 5% Perpetual Cumulative Convertible Preferred Stock (Liquidation Preference $50.00 Per Share) who elect to convert their shares of preferred stock to shares of the Company’s common stock subject to the terms of the offer, the Company is providing the following financial information to holders of the preferred stock.

The Company’s book value per common share as of September 30, 2005 was $18.09. In addition, below is the Company’s income per common share from continuing operations, basic and diluted, and ratio of earnings to combined fixed charges and preference dividends for the periods indicated.

	Years Ended December 31,												Nine Months Ended
	2000			2001		2002			2003		2004		September 30, 2005
Basic earnings (loss) per common share from continuing operations	$	(0.33	)	$	0.15	$	(0.05	)	$	0.19	$	1.91	$	0.37
Diluted earnings (loss) per common share from continuing operations	$	(0.33	)	$	0.15	$	(0.05	)	$	0.19	$	1.78	$	0.37
Ratio of earnings to combined fixed charges and preference dividends (1)		—			1.04x		—			—		2.54x		1.33x

(1) Ratio of earnings to combined fixed charges and preference dividends is computed on a total enterprise basis including our consolidated subsidiaries, plus our share of significant affiliates accounted for on the equity method that are 50% or greater owned or whose indebtedness has been directly or indirectly guaranteed by us. Earnings consist of income (loss) from continuing operations before income taxes and are adjusted to include fixed charges (excluding capitalized interest). Fixed charges consist of interest incurred on indebtedness, the portion of operating lease rentals deemed representative of the interest factor and the amortization of debt expense. Preference dividends are the amount of pre-tax earnings required to pay dividends on our outstanding preferred stock and Arch Western Resources, LLC’s preferred membership interest. In 2000, 2002 and 2003, combined fixed charges and preference dividends exceeded earnings by $16.7 million, $22.3 million and $2.9 million, respectively.

Item 8.01 Other Events.

     On December 16, 2005, Arch Coal, Inc. announced an amendment and extension of its previously announced offer to pay a premium to holders of any and all of its 5% Perpetual Cumulative Convertible Preferred Stock (Liquidation Preference $50.00 Per Share) who elect to convert their shares of preferred stock to shares of the Company’s common stock subject to the terms of the offer. A copy of Arch Coal, Inc.’s press release is attached hereto as Exhibit 99.1.

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Exhibit Index begins on page 5.

Item 9.01 Financial Statements and Exhibits.

     (c) Exhibits.

     The following Exhibit is filed with this Current Report on Form 8-K:

Exhibit No.	Description
99.1	Press Release dated December 16, 2005

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SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: December 16, 2005	ARCH COAL, INC
	By:	/s/ Robert J. Messey
		Robert J. Messey
		Senior Vice President and Chief Financial Officer

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Exhibit Index begins on page 5.

EXHIBIT INDEX

Exhibit No.	Description
99.1	Press Release dated December 16, 2005.

Page 5 of 5 pages.

EX-99.1

Exhibit 99.1

News from
Arch Coal, Inc.

FOR FURTHER INFORMATION:
Media — Kim Link (314) 994-2936
FOR IMMEDIATE RELEASE
December 16, 2005

Arch Coal Amends and Extends Offer for Its 5% Perpetual

Cumulative Convertible Preferred Stock

ST. LOUIS (December 16, 2005) — Arch Coal, Inc. (NYSE: ACI) today amended its previously announced offer to pay a premium to holders of any and all of its 5% Perpetual Cumulative Convertible Preferred Stock who elect to convert their preferred stock to shares of the company’s common stock subject to the terms of the offer. Arch Coal also extended the conversion offer so that it will expire at 12:00 midnight, Eastern Standard Time, on Friday, December 30, 2005, unless extended or earlier terminated.

As amended, in addition to the shares of common stock to be issued upon conversion pursuant to the documents governing the terms of the preferred stock, holders who surrender their preferred stock on or prior to the expiration date will receive a per share premium in an amount of shares of common stock valued at $3.50, as determined by dividing (i) $3.50 by (ii) the volume-weighted average of the reported sales prices on the New York Stock Exchange of the common stock during the 10 trading days ending at the close of the second trading day prior to the expiration of the conversion offer.

The offer is being made pursuant to an offering circular, as supplemented, and related documents, each of which has been disseminated to holders of the preferred stock. The completion of the offer is subject to conditions described in the conversion offer documents. Subject to applicable law, Arch Coal may waive the conditions applicable to the offer or extend or otherwise amend the offer.

This press release is not an offer to convert, or a solicitation of an offer to convert, any preferred stock. The conversion offer is being made only on the terms and subject to the conditions described in the offering circular and related documents, which will be distributed to holders of preferred stock. Copies of the offering circular, including supplements thereto, and related documents have been filed with the Securities and Exchange Commission as exhibits to a Schedule TO. Holders of preferred stock may address questions about the conversion offer or requests for copies of the offering circular and related documents to American Stock Transfer & Trust Company by calling toll-free at (877) 248-6417.

St. Louis-based 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 provides the fuel for approximately 7% of the electricity generated in the United States.