Mel Ferrer

as Patriarch

as Cornelius A. Woaegen, president of GTI

as David Mendelssohn

as General Murchison

as Professor Carter

as Joshua

as Dr. Walker

as Radcliffe (US version)

as Vera Husband

as Dr. Sidney Coleman

as King Eurich

as Dr. Robert Cook

as Professor Henry Douglas

as Harvey Wood

as Van Gould

as Police superintendent

as District Attorney Mannino

as Mel Fields

as Massimo Oderisi

as French-Canadian Radio Speaker (voice) (uncredited)

as Rudy DeMeyer

as Cleander

as Dr. Jekyll & Mr. Hyde (uncredited)

as Maj. Gen. Robert Haines

as Philip Allan

as Leopoldo De Karnstein

as Benson Thacker

as Robert Cohn

as Le comte Henri de Chevincourt

as Prince Andrei Bolkonsky

as Capt. Alfred Westerman

as Arthur

as Paul Berthalet

as Noel, Marquis de Maynes

as Frenchy Fairmont

as Gobby

as Dr. Scott Mason Carter

as Father Serra (uncredited)