Roy Scheider

Character: Dr. Heywood Floyd

John Lithgow

Character: Dr. Walter Curnow

Helen Mirren

Character: Tanya Kirbuk

Bob Balaban

Character: Dr. R. Chandra

Keir Dullea

Character: Dr. David Bowman

Douglas Rain

Character: HAL 9000 (voice)

Madolyn Smith Osborne

Character: Caroline Floyd

Savely Kramarov

Character: Dr. Vladimir Rudenko

Taliesin Jaffe

Character: Christopher Floyd

James McEachin

Character: Victor Milson

Mary Jo Deschanel

Character: Betty Fernandez

Ilya Baskin

Character: Maxim Brailovsky

Dana Elcar

Character: Dimitri Moisevitch

Oleg Rudnik

Character: Dr. Vasili Orlov

Natasha Shneider

Character: Irina Yakunina

Vladimir Skomarovsky

Character: Yuri Svetlanov

Victor Steinbach

Character: Nikolaj Ternovsky

Candice Bergen

Character: SAL 9000 (voice)

Gene McGarr

Character: Commercial Announcer

Herta Ware

Character: Jessie Bowman

Jan Tříska

Character: Alexander Kovalev

Larry Carroll

Character: Anchorman on TV

Cheryl Carter

Character: Nurse

Ron Recasner

Character: Hospital Neurosurgeon

Robert Lesser

Character: Dr. Hirsch

Delana Michaels

Character: Commercial Announcer

Arthur C. Clarke

Character: Man on Park Bench (uncredited)