Sir Laurence Olivier took the role of 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 Szell. However, because Olivier at the time was riddled with cancer, he was uninsurable, so Paramount Pictures refused to use him. In desperation, 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.

Roy Scheider received the book while filming Jaws (1975). He finished the book in one night. The next day, he told the man who had given him the book that it was a great book, and would make a great movie, though he was disappointed that the character he found most interesting, Henry Levy, died halfway through the book. Only a year later, he was playing the role.

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.'"

A story circulated for a long time that Dustin Hoffman (being a "method actor") stayed up all night to play a character who has stayed up all night. Arriving on the set, Sir Laurence Olivier asked Hoffman why he looked the way he did. Hoffman told him, to which Olivier replied in jest, "Why not try acting? It's much easier." Hoffman repeatedly denied the story, and finally cleared up the matter in 2004. The torture scene was filmed early in the morning, Hoffman was going through a divorce from his first wife and was depressed, and had spent the previous two nights partying hard. Hoffman told Olivier this and his comment related to his lifestyle and not his "method" style of acting.

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'd actually be out of breath."

Sir Laurence Olivier was so afraid that he would accidentally hurt Dustin Hoffman while filming the torture scene, that he would constantly ask Hoffman if he was all right after shooting a take. As a joke, Hoffman tried to make Olivier think that he had really hurt him by screaming in a very convincing and unexpected manner.

In the novel, Doc meets one of his rivals as an assassin at Los Angeles International Airport, and the two talk. Doc realizes that all assassins such as himself eventually are killed and, indeed, the fellow assassin is soon murdered in an airport restroom. Doc nearly kills the men who did it, which shows his behavior is becoming erratic and he may too soon be terminated. The incident makes Doc realize that the one thing he wants in his life is to die in the company of someone who loves him, not in the sordid manner of his fellow assassin. This desire explains Doc's motivation of going to his brother Babe after being mortally wounded, an action which is misunderstood by Szell and Janeway. In the movie, Doc's near murder of the killers of his fellow assassin was filmed, but cut, which also likely eliminated the motivation of why Doc goes to Babe.

According to "Adventures in the Screen Trade", at one point in rehearsal, Sir Laurence Olivier asked William Goldman if he could change a line slightly, and called Goldman "Bill" while doing so. Goldman describes it as the high point of his career.

On the last day of shooting, Sir Laurence Olivier visited Dustin Hoffman at his house, bringing with him "The Complete Works of William Shakespeare" as a gift. He then proceeded to read scenes from several of the plays, much to Hoffman's delight. Hoffman credits the story about his conflict with Olivier to general malice on the part of Writer William Goldman, who did not take kindly to the fact that Hoffman had persuaded Director John Schlesinger to change the ending of Goldman's book.

According to Producer Robert Evans, in a rare twist, all his first choices for the film's leads, Dustin Hoffman, Sir Laurence Olivier, Roy Scheider, William Devane, and Marthe Keller, were all cast in the roles for which were envisioned.

Although not particularly a fan of William Goldman's original novel, Dustin Hoffman took the role so that he could work with John Schlesinger again (the two had previously collaborated on Midnight Cowboy (1969)). He had also heard that Al Pacino was interested in the role and wanted to beat him to it.

The torture scene was shortened after preview audiences were taken sick.

The movie's line "Is it safe?" was voted as the #70 movie quote by the American Film Institute (out of 100).

Although he was playing a graduate student, Dustin Hoffman was thirty-eight-years-old at the time of filming, which really doesn't matter, because people have been known to attend college well into adulthood.

When Babe (Dustin Hoffman) is running up the stairs outside on campus, he asks another student which room Professor Biesenthal's class is in. That student was played by John Heard (uncredited).

The outtakes reveal a couple of things. First, Sir Laurence Olivier had trouble using the large switchblade made for his character Szell. Often, he would try to activate it and the blade would not come out. Second, several actors enjoyed imitating the unique speech patterns of Producer Robert Evans. Dustin Hoffman used that imitation for his performance in Wag the Dog (1997).

During the torture scene, Szell indicates he is afflicted with alexia. Alexia is a brain disorder in which a person is unable to understand written words. Sometimes also called acquired dyslexia, it refers specifically to the loss, usually in adulthood, of a previous ability to read.

Joseph Spah (billed as Ben Dova), portraying Szell's brother, is the driver of the stalled car involved in the opening car-truck collision. Mr. Spah was a survivor of the Hindenburg disaster.

The first movie to use a Steadicam that saw theatrical release. It was the second feature film where Garrett Brown used his new invention, the first being Bound for Glory (1976), however this film was released first. He would receive an Academy Award in 1978 for this system.

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."

Sir Laurence Olivier played the character Dr. Christian Szell, based on Dr. Josef Mengele, head S.S. Doctor of Auschwitz, who was in hiding in South America when this movie was produced. In The Boys from Brazil (1978), Olivier played Ezra Lieberman, a Jewish Nazi hunter (based on Simon Wiesenthal), who tracks down Dr. Josef Mengele (played by Gregory Peck). Olivier received Academy Award nominations for both roles.

Although William Goldman adapted the script from his own novel, Robert Towne did an uncredited re-write for the climax.

An eight minute and thirty second sequence was shot with Doc (Roy Scheider) fighting some men who kill a spy colleague of his. It was later cut. William Goldman speculated it was cut because it was violent. He felt it was a grievous excision, one to the detriment of the movie. With the scene missing, Doc's character seems less flawed than he really is.

There are two photos of long-distance runner legends in Babe's room: one is of Abebe Bikila, who is also seen running in the beginning of the movie. The other is of Finnish runner Paavo Nurmi, a nine-time Olympic gold medalist.

Although the first preview of the movie was successful, the second one which was shown in San Francisco did not go well. The audience complained about all the violence in the movie, so Director John Schlesinger and Editor Jim Clark deleted a scene near the beginning of the movie in which Doc fights with two assassins who killed his friend, removed a graphic and gory close-up of Szell disemboweling Doc with his wrist blade, and cut both of the torture scenes heavily. Graphic insert shots from the torture scene which were filmed by Clark were removed. Some photos, such as original lobby cards and still shots show Szell torturing Babe longer with dental instruments in the first torture scene and actual on-screen drilling of Babe's tooth in the second torture scene.

Although his proper first name is not listed in any of the credits, Dustin Hoffman's character Babe does speak his full given name once: during police questioning after the murder of his brother, he is asked his name, and shouts out "Thomas Babington Levy". He also quickly identifies himself as "Tom Levy" when desperately trying to buzz into his neighbor's apartment building after being chased, ultimately having to identify himself as "the Creep", since no one there knows him by his real name.

Sir Laurence Olivier's salary was one hundred thirty-five thousand dollars.

Director John Schlesinger envisioned a cast of Al Pacino, Julie Christie, and Sir Laurence Olivier. Pacino has said that the only actress he had ever wanted to work with was Christie, who he claimed was "the most poetic of actresses". Producer Robert Evans, who disparaged Pacino as "The Midget" when Francis Ford Coppola wanted him for The Godfather (1972), and had thought of firing him during the early shooting of the now-classic movie, vetoed Pacino for the lead. Instead, Evans insisted on the casting of the even shorter Dustin Hoffman. Christie, who was notoriously finicky about accepting roles, even in prestigious, sure-fire material, turned down the female lead, which was then taken by Marthe Keller. Of his dream cast, Schlesinger only got Olivier, who was nominated for a Best Actor in a Supporting Role Oscar.

John Schlesinger had wanted Charlotte Rampling for the role of Elsa. Marthe Keller starred in a series of high-profile movies, including Black Sunday (1977), Bobby Deerfield (1977), and Fedora (1978) around this time, but they failed to click with audiences and her Hollywood career was short-lived.

The role of Szell's brother was portrayed by Ben Dova. "Ben Dova" was the stage name for actor, comedian and acrobat Joseph Spah. Spah was a survivor of the Hindenburg disaster of 1937. He was not only a survivor, but a person of interest. During the flight, he was granted access to the interior of the airship, off-limits to passengers so he could feed and walk his dog who was kept in the cargo area. Because of this, he was heavily investigated after the disaster, but eventually exonerated. In every documentary, movie, and literature about the Hindenburg, Joseph Spah is prominently featured.

In the documentary The Magic of Hollywood... Is the Magic of People (1976), Dustin Hoffman recalls that Sir Laurence Olivier got inspiration for the torture scene from seeing a gardener pruning roses shortly before shooting. Olivier realized that Szell at that moment saw himself as a craftsman, using tools with skill.

When Babe (Dustin Hoffman) comes in from a run, you can see a book titled "Corbitt" on his table. Corbitt was an American marathoner in the 1950s who was also from New York City and who also taught at Columbia University, which Babe attends in the movie.

Dr. Christian Szell was ranked as villain #34 on the American Film Institute's "100 Years...100 Heroes and Villains" list. The film itself was ranked #50 on the "100 Years...100 Thrills" list. The torture scene was named #65 on Bravo's 100 Scariest Movie Moments.

Although this movie takes place in New York City, at least two sequences were filmed in Los Angeles: the scene where Roy Scheider meets Sir Laurence Olivier was filmed in front of the red steps statue in downtown Los Angeles in the Arco Plaza; and the library scene where Dustin Hoffman meets Marthe Keller was filmed at the Doheny Library on the University of Southern California campus. Coincidentally, Hoffman filmed scenes on the same campus for The Graduate (1967).

During rehearsals, Hoffman famously objected to his character having a flashlight near him in the abduction scene. He just felt it was out of character. Schlesinger eventually managed to persuade him that it would make the scene more interesting cinematically. William Goldman, who was present at the the time, had the impression it was because Hoffman did not want to appear to be chicken.

The last commercially successful movie directed by John Schlesinger.

This movie is mentioned at length by Raymond Reddington (James Spader) in The Blacklist (2013) season two, episode twenty, "Quon Zhang". He has trouble recalling William Devane.

Robert Shaw was considered for the role of Peter Janeway.

The often quoted, and popular, line, "Is it safe?", along with the torture scene, was briefly spoofed in Gremlins 2: The New Batch (1990) and Hot Shots! (1991).

Jean-Pierre Aumont and George Cukor were among those who were on the shortlist for Dr. Christian Szell.

John Schlesinger's first thriller.

Final theatrical movie of Madge Kennedy's (Lady in Bank).

Sir Laurence Olivier received his only Best Actor in a Supporting Role Academy Award nomination for his role as Dr. Christian Szell. All of his other acting nominations were for Best Actor in a Leading Role.

When Dr. Szell first appears, he is listening to a record of a German classical song accompanied by piano. The song is "Der Neugierige" ("The Questioner" or "The Curious One") by Franz Schubert, from the song-cycle "Die schöne Müllerin" ("The Pretty Miller-Girl"). The singer is lyric tenor Fritz Wunderlich, whose recordings of German art songs of this type are generally considered the gold standard for this genre, much studied and imitated by lesser singers and students. Born in 1930, Wunderlich was a child, and an early teen, during the time of the Third Reich. He died before the movie's action occurs, when he was 36 years old; had he lived, he probably would not have appreciated Dr. Szell's admiration, because his (Wunderlich's) father had committed suicide after clashes with the Nazis caused him to lose his job.

Sir Laurence Olivier's Best Actor in a Supporting Role Oscar nominated performance was the only one in the category not in a Best Picture nominee that year.

Two of the young hoods who help Babe by breaking into his apartment, Tito Goya and Church Ortiz, would play prisoners the following year in Short Eyes.

Theatrical movie debut of Ben Dova (Szell's brother).

The interior of the water works at Central Park was constructed across two sound stages at Paramount Studios in Hollywood.

One of the other graduate students in Professor Biesenthal's class is played by Mark L. Taylor (uncredited).

Paramount paid $500,000 plus profit participation to William Goldman for the film rights to his novel.

Screenwriter Robert Towne did an uncredited rewrite on the ending climactic waterworks scene between Babe and Szell. Towne's rewrite had Babe force Szell to eat the diamonds. Towne also changed Szell's death to self-inflicted.

This movie changes the novel's ending, and Goldman thought the new ending was "shit". He felt the way it ended, it left out two important plot clarifications. In the novel, Babe leads Szell by gunpoint to Central Park and shoots him multiple times, subsequently lecturing him. He then throws the diamonds away and is quietly led away by a policeman.

Author Christopher Pike called this movie interesting in his novel "The Eternal Dawn", meaning he must be a fan, but instead of citing the famous drill scene as the best, it's the scene after when Dustin Hoffman is rescued by a friend, who's secretly in league with Sir Laurence Olivier, and drives him right back.

Body count: eleven. (In chronological order: Szell's brother, Rosenbaum, Le Clerc, Chen, Doc, Karl, Erhard, Elsa, Janeway, the jeweler, and finally Szell).

William Goldman, who wrote the book and the screenplay, wrote a sequel. It's called "Brothers" and picks up the story of Scylla, who survives his apparently fatal wounds.