Sir Laurence Olivier took the role of Dr. Szell in part to leave a great deal of money to his wife and children, as he expected to die from the cancer that afflicted him throughout production. He performed the role while undergoing treatment for his cancer, which included heavy doses of painkillers to allow him to work every day. The pain medication affected his memory, and at times Olivier could not remember more than one or two of his lines at a time. In a testament to his fierce concentration, his performance garnered rave reviews and an Oscar nomination, and despite working under such aggressive medical treatment, he experienced a full recovery, allowing him to enjoy the success of this movie, and a series of leading roles that followed.
Producer Robert Evans was set upon getting Sir Laurence Olivier to play the role of Dr. Szell. However, because Olivier at the time was riddled with cancer, he was uninsurable, so Paramount Pictures refused to use him. Desperate, Evans called his friends Merle Oberon and David Niven to arrange a meeting with the House of Lords (the upper body of the British parliament). There, he urged them to put pressure on Lloyd's of London to insure Britain's greatest living actor. The ploy succeeded, and a frail Olivier started working on this movie. In the end, not only did he net an Oscar nomination for Best Actor in a Supporting Role, but his cancer also went into remission. Olivier lived on for another thirteen years.
During the scene where the heavies try to drown Dustin Hoffman in the bathtub, Hoffman (always the method actor) insisted upon being made to stay underwater as long as possible to make it real. Several takes were done and Hoffman insisted on being kept down longer in the water. By the end of the scene, he had to be given oxygen. In his own words "I said 'Don't press on my Adam's apple, but try to really hold me under. Let me see how long I can stay under. Let me see if I can fight you. Let me see what happens.'"
Dustin Hoffman lost fifteen pounds for this role. He ran up to four miles a day to get into shape for playing the role. He would never come into a scene and fake the breathing. According to Producer Robert Evans, Hoffman "would run, just for a take, he would run for a half-mile so he came into the scene, he would actually be out of breath."
Abebe Bikila is shown in flashbacks running in and winning the 1960 Olympic Marathon shoeless. After the race, when asked why he had run barefoot, he replied "I wanted the whole world to know that my country, Ethiopia, has always won with determination and heroism." Some audiences and critics misidentified Abebe Bikila and thought it was the more well-known African American athlete Jesse Owens.