Gregory Peck as Dr. Josef Mengele

Laurence Olivier as Ezra Lieberman

James Mason as Eduard Seibert

Lilli Palmer as Esther Lieberman

Uta Hagen as Frieda Maloney

Steve Guttenberg as Barry Kohler

Denholm Elliott as Sidney Beynon

Rosemary Harris as Mrs. Doring

John Dehner as Henry Wheelock

John Rubinstein as David Bennett

Anne Meara as Mrs. Curry

Jeremy Black as Jack Curry / Simon Harrington / Erich Doring / Bobby Wheelock

Bruno Ganz as Professor Bruckner

Walter Gotell as Mundt

David Hurst as Strasser

Wolfgang Preiss as Lofquist

Michael Gough as Mr. Harrington

Joachim Hansen as Fassler

Sky du Mont as Dietrich Hessen

Carl Duering as Trausteiner

Linda Hayden as Nancy

Richard Marner as Doring

Georg Marischka as Gunther

Günter Meisner as Farnbach

Prunella Scales as Mrs. Harrington

Raul Faustino Saldanha as Ismael

Jürgen Andersen as Wolfgang Kleist

Mervyn Nelson as Stroop

David Brandon as Schmidt

Monica Gearson as Gertrud

Wolf Kahler as Arno Schwimmer

Gerti Gordon as Berthe

Joseph Oliveira as German Newspaper Boy (uncredited)