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 23, 2003
                                                      (December 22, 2003)

                                 Arch Coal, Inc.
             (Exact name of registrant as specified in its charter)

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

            One CityPlace Drive, Suite 300, St. Louis, Missouri 63141
               (Address of principal executive offices) (Zip code)

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

                               Page 1 of 4 pages.
                         Exhibit Index begins on page 4.

Item 5 Other Events.

     On December 22, 2003, Arch Coal, Inc. (the "Company"),  announced via press
release that it sold a portion of its  investment in Natural  Resource  Partners
L.P. to private  investment groups for a purchase price of $115 million.  A copy
of the Company's press release is attached hereto and is incorporated  herein by
reference in its entirety.

Item 7.  Exhibits.

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

               Exhibit No.                        Description

                      99            Press Release dated as of December 22, 2003.

                               Page 2 of 4 pages.
                         Exhibit Index begins on page 4


     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 23, 2003                 ARCH COAL, INC.

                                          By:/s/ Janet L. Horgan
                                          Janet L.Horgan
                                          Assistant General Counsel and
                                                 Assistant Secretary

                               Page 3 of 4 pages.
                         Exhibit Index begins on page 4.

                                  EXHIBIT INDEX

Exhibit No.                 Description
99                         Press Release dated as of December 22, 2003

                               Page 4 of 4 pages.

                                                                     Exhibit 99
News from
Arch Coal, Inc.
                                                        FOR FURTHER INFORMATION:

                                                                  Deck S. Slone
                                                                 Vice President,
                                                   Investor and Public Relations
                                                                  (314) 994-2717

                                                           FOR IMMEDIATE RELEASE
                                                              December 22, 2003

Arch Coal, Inc. sells a portion of its investment in NRP for $115 million

     St.  Louis  - Arch  Coal,  Inc.  (NYSE:ACI)  today  announced  that  it had
completed  the  sale of its 4.8  million  subordinated  units,  general  partner
interests and incentive  distribution  rights in Natural Resource  Partners L.P.
(NYSE:NRP)  to  private  investment  groups  led by  Corbin J.  Robertson,  Jr.,
chairman  and chief  executive  officer  of NRP,  for a  purchase  price of $115
million.  The  transaction  does not include the 2.9 million common units of NRP
owned by Arch.

     "Through the formation of Natural  Resource  Partners,  its initial  public
offering,  and  now  the  sale  of our  subordinated  units,  we  have  unlocked
tremendous value for our  shareholders,"  said Steven F. Leer,  Arch's president
and chief executive officer.  "This transaction is part of a long-term effort to
monetize  the value of assets that were  previously  undervalued  on our balance
sheet,  while providing us with a timely infusion of cash that can be applied to
the proposed acquisition of Triton Coal Company."

     In October  2002,  Arch  contributed  assets to NRP that were valued at $85
million on its balance  sheet.  Through the sale of units at the time of the IPO
and the transaction described above, Arch has sold a portion of its stake in NRP
for total proceeds of $148 million.  "Arch's  remaining 2.9 million common units
have a current  market value of more than $110  million,  and these common units
continue to represent an excellent investment," Leer said.

     In addition to this continuing ownership position, NRP will remain a valued
business  partner,  according to Leer. "We look forward to continuing our strong
and successful relationship with NRP in the future," Leer added.

     Including the proceeds from the  transaction,  Arch now has cash on hand of
more than $220 million.  "Our strong cash position should enable us to finance a
significant  portion  of Triton - a large and  highly  strategic  acquisition  -
without incurring  significant  additional  indebtedness," Leer said. The Triton
acquisition is currently undergoing review by the Federal Trade Commission.

     As a result  of the sale of its  subordinated  units  and  general  partner
interest in NRP, Arch expects to recognize a pre-tax gain of $74.2  million,  of
which $42.7  million will be  recognized  in the fourth  quarter of 2003 and the
remainder will be deferred until future periods. Deferred gains, including those
from the sale of NRP units at the time of the IPO, are expected to be recognized
as follows:  $12.5 million in 2004;  $6.7 million in 2005; $4.1 million in 2006;
and the remainder in the period 2007 through 2012.

     Partially  offsetting  the expected  fourth  quarter gain will be a pre-tax
charge  of  $16.7  million  related  to  the  payout  of  a  long-term  employee
compensation  plan based on the performance of the company's stock over the past
four years.

     Natural Resource Partners L.P. is headquartered in Houston, Texas, with its
operations headquarters in Huntington, W.Va. NRP is a master limited partnership
that is  principally  engaged  in the  business  of  owning  and  managing  coal
properties  in the three  major coal  producing  regions  of the United  States:
Appalachia, the Illinois Basin and the Powder River Basin.

     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 6% of
the electricity generated in the United States.

     Forward-Looking Statements:  Statements in this press release which are not
statements of historical  fact are  forward-looking  statements  within the safe
harbor provision of the Private Securities  Litigation Reform Act of 1995. These
forward-looking  statements are based on information currently available to, and
expectations and assumptions  deemed  reasonable by, the Company.  Because these
forward-looking  statements  are  subject  to various  risks and  uncertainties,
actual results may differ  materially  from those  projected in the  statements.
These expectations,  assumptions and uncertainties include the completion of the
Companys   acquisition   of  Triton  Coal   Company  and  the  other  risks  and
uncertainties  which are described  from time to time in the  companys  reports
filed with the Securities and Exchange Commission.