EXHIBIT 3

                           [LETTERHEAD OF GLENCORE AG]

Credit Suisse First Boston LLC
Eleven Madison Avenue
New York, New York 10010
Morgan Stanley & Co. Incorporated
1585 Broadway
New York, NY 10036

March 25, 2004

Dear Sirs and Mesdames:

      The undersigned understands that Credit Suisse First Boston LLC ("CSFB")
and Morgan Stanley & Co. Incorporated ("Morgan Stanley") propose to enter into
an Underwriting Agreement (the "Underwriting Agreement") with Century Aluminum
Company, a Delaware corporation (the "Company") and possibly Century Aluminum
Employees Retirement Plan and the Century Aluminum of West Virginia, Inc. Hourly
Employees Pension Plan (together, the "Selling Shareholders"), providing for the
public offering (the "Public Offering") by the several Underwriters, including
CSFB and Morgan Stanley (the "Underwriters"), of shares (the "Shares") of the
Common Stock, $.01 par value of the Company (the "Common Stock").

      To induce the Underwriters that may participate in the Public Offering to
continue their efforts in connection with the Public Offering, the undersigned
hereby agrees that, without the prior written consent of CSFB and Morgan Stanley
on behalf of the Underwriters, it will not, during the period commencing on the
date hereof and ending 90 days after the date of the final prospectus relating
to the Public Offering (the "Prospectus"), (1) offer, pledge, sell, contract to
sell, sell any option or contract to purchase, purchase any option or contract
to sell, grant any option, right or warrant to purchase, lend, or otherwise
transfer or dispose of, directly or indirectly, any shares of Common Stock or
any securities convertible into or exercisable or exchangeable for Common Stock,
or (2) enter into any swap or other arrangement that transfers to another, in
whole or in part, any of the economic consequences of ownership of the Common
Stock, whether any such transaction described in clause (1) or (2) above is to
be settled by delivery of Common Stock or such other securities, in cash or
otherwise. The foregoing sentence shall not apply to (a) the sale of any Shares
to the Underwriters pursuant to the Underwriting Agreement, (b) transactions
relating to shares of Common Stock or other securities acquired in open market
transactions after the completion of the Public Offering, (c) transfers of
shares of Common Stock as bona fide gifts; provided that (i) the transferee
agrees to enter into a lock-up letter substantially in the form of this Lock-Up
Agreement and (ii) the undersigned shall not be required to, and shall not
voluntarily, file a report on Form 4 under Section 16(a) of the Securities
Exchange Act of 1934 reporting a reduction in beneficial ownership of shares of
Common Stock during the restricted period referred to in the foregoing sentence
and (d) sales or other dispositions of shares of Common Stock to the Company to
discharge tax withholding obligations resulting from the vesting of performance
shares during the term of the Lock-Up Agreement; provided that (i) the
undersigned is listed on Schedule I hereto and (ii) the aggregate



number of shares withheld by the Company for all persons listed on Schedule I
hereto shall not exceed 100,000 shares of Common Stock. In addition, the
undersigned agrees that, without the prior written consent of CSFB and Morgan
Stanley on behalf of the Underwriters, it will not, during the period commencing
on the date hereof and ending 90 days after the date of the Prospectus, make any
demand for or exercise any right with respect to, the registration of any shares
of Common Stock or any security convertible into or exercisable or exchangeable
for Common Stock. The undersigned also agrees and consents to the entry of stop
transfer instructions with the Company's transfer agent and registrar against
the transfer of the undersigned's shares of Common Stock except in compliance
with the foregoing restrictions.

      The undersigned understands that the Company and the Underwriters are
relying upon this Lock-Up Agreement in proceeding toward consummation of the
Public Offering. The undersigned further understands that this Lock-Up Agreement
is irrevocable and shall be binding upon the undersigned's heirs, legal
representatives, successors and assigns.

      Whether or not the Public Offering actually occurs depends on a number of
factors, including market conditions. Any Public Offering will only be made
pursuant to an Underwriting Agreement, the terms of which are subject to
negotiation between the Company and the Underwriters. If for any reason the
Underwriting Agreement shall be terminated prior to the Closing Date (as defined
in the Underwriting Agreement), the agreement set forth above shall likewise be
terminated.

                              Very truly yours,

                              GLENCORE AG


                              /s/ Zbynek E. Zak      /s/ Lotti Grenacher Hagmann
                              -----------------      ---------------------------
                              Zbynek E. Zak          Lotti Grenacher Hagmann
                              Director               Officer



                                   Schedule I

Craig A. Davis
Gerald J. Kitchen
David W. Beckley
E. Jack Gates
Daniel J. Krofcheck
Steve Schneider
Peter C. McGuire
John C. Fontaine
John P. O'Brien
Robert E. Fishman
William R. Hampshire
Roman A. Bninski
Stuart M. Schreiber
Willy R. Strothotte
Glencore International AG