Gregory Peck was upset by the extremely negative reactions to his performance. He later said, "I felt, Laurence Olivier felt, friends of mine like Walter Matthau and Jack Lemmon felt, that I was good in this part. Some critics seem unwilling to accept actors when they break what they think is the mold or the image."
Publicity for the film stated that this was the first villainous role of Gregory Peck's career. Peck felt that his portrayal of Nazi war criminal Dr. Josef Mengele was the only completely unsympathetic role that he ever performed. However, Peck's characters in Duelo al sol (1946), Moby Dick (1956), and The Bravados (1958) have often been described as villains.
In a promotional interview with Roger Ebert, James Mason explained that he had hoped to get either Laurence Olivier's or Gregory Peck's role, and was disappointed to be offered neither, but then was contacted about the subsidiary role of Seibert: "They'd found that when Dr. Mengele was in Paraguay, he had no one to talk to so they fleshed out the other Nazi, and he fell into my lap. It was convenient, it was acceptable, I could even make sense of the character, and besides, it was four weeks work in Portugal, where I'd never been before."
Laurence Olivier received an Oscar® nomination for Best Actor for his role in this movie, playing a Jewish man who hunts Josef Mengele and other Nazi war criminals. His most recent Oscar nomination for Best Actor in a Supporting Role prior to this was for Maratón de la muerte (1976) in which he played Dr. Christian Szell, a Nazi war criminal based on Dr. Josef Mengele. For this film, Olivier received his tenth and final Academy Award® nomination making him the most nominated actor up to that point. His record was later surpassed by Jack Nicholson with 12 nominations.
Laurence Olivier was in poor health during filming, having recently undergone surgery to remove kidney stones.