1 EXHIBIT NO. 99.1: PRESS RELEASE OF ALCAN ALUMINIUM LIMITED, DATED APRIL 21, 2000 MONTREAL, CANADA - APRIL 21, 2000 - Alcan Aluminium Limited (NYSE,TSE : AL) advises that the applicable waiting period under U.S. antitrust regulations with respect to the proposed Alcan-algroup merger has expired. Consequently, there is no U.S. antitrust regulatory barrier to proceeding with the transaction. The proposed Alcan-algroup merger has already received approval from the European Commission, subject to a number of conditions as stated in their March 14th 2000 decision. -30- MEDIA RELATIONS INVESTOR RELATIONS Marc Osborne Alan G. Brown (514) 848-1342 (514) 848-8368 5