Frank Sinatra broke one of his fingers when he hit the table, which was real and not a break-away prop, in the fight sequence with Henry Silva. Due to ongoing filming commitments, he could not rest or bandage his hand properly, causing the injury to heal incorrectly. It caused him chronic discomfort for the rest of his life.

Frank Sinatra refers to Orestes and Clytemnestra when he is talking to Laurence Harvey. Clytemnestra was the wife of Agamemnon (King of the Ancient Greek kingdom of Mycenae) who, with her lover Aegisthus, murdered him and took over the throne. Orestes, the son of Clytemnestra, later killed them both.

Frank Sinatra wanted Lucille Ball for the role of Mrs. Iselin which was played by Angela Lansbury.

John Frankenheimer opted to direct this movie after plans to film author Richard Yates's 1961 novel "Revolutionary Road" failed to materialize. The latter would not be filmed until Revolutionary Road.

George Axelrod copied the lecture about hydrangeas verbatim from a seed catalogue.

Angela Lansbury was thirty-six at the time of filming, only three years older than Laurence Harvey, who played her son.

A scene where Laurence Harvey jumps in Central Park lake was shot on the coldest day in 30 years. They had to break the foot-thick ice on the lake with a bulldozer before the scene could be shot.

By his own admission Frank Sinatra's best work always came in the first take. John Frankenheimer always liked the idea of using the freshness of a first take - so nearly all of the key scenes featuring Sinatra are first takes, unless a technical problem prevented them being used.

Contrary to popular belief, the film was not pulled from circulation following the 1963 assassination of President John F. Kennedy. It made its American television debut on The CBS Thursday Night Movies in September 1965 (source: Broadcasting magazine), and was repeated on that network later that season. Only when the rights reverted to Frank Sinatra in 1972 did the film disappear from view, although even then turning up for third and fourth network showings on NBC in spring 1974 (source: TV Guide) and summer 1975 (source: Variety). Sinatra's neglect in keeping the film in distribution gave rise to the legend that it was suppressed because of its alleged role in Lee Harvey Oswald's assassination of the 35th president. The legend was further perpetuated when Sinatra, in alliance with MGM/UA, re-released the film to theaters in 1988. When the rumor was debunked in an article in Films in Review, another myth, one claiming that Sinatra and UA had a dispute about the profits, took its place. The myth survives to this day, but it is pure fiction.

Famous for his use of innovative camera angles, director John Frankenheimer was widely acclaimed for a shot that is slightly out of focus. John Frankenheimer said that rather than the shot being evidence of inspiration, it was an accident and merely the best take for actor Frank Sinatra.

In Richard Condon's novel, the relationship between Mrs. Iselin and her son Raymond is more explicitly incestuous, complete with a bed scene. Director John Frankenheimer and screenwriter George Axelrod wanted to include that element, but reduced it to the less-than-motherly kiss that Mrs. Iselin plants on Raymond's lips. To appease the censors, Frankenheimer instructed Angela Lansbury to put her hand between their mouths and the camera during the kiss to obscure what she was doing a bit. By time of Jonathan Demme's The Manchurian Candidate, the incestuous content between the mother and son shown on screen had been reduced even more, so that the camera cuts away before she kisses her son on the lips, only leaving the implication of that relationship between them.

In an interview with 'Starlog' magazine in 1990, Henry Silva said "no one was doubled" in the fight scene between him and Frank Sinatra.

In joke: During the prologue set in 1952, one of the bar girls reads an old movie magazine with a cover shot of Tony Curtis and Janet Leigh, who plays the female lead in this film.

In the scene where Frank Sinatra gives the all-queens deck of cards to Laurence Harvey, Sinatra is out of focus. He had trouble recreating his performance, so director John Frankenheimer left the footage as is. Audiences weren't bothered; they interpreted it as Harvey's blurred perspective.

It took a full week to film the opening dream sequence. Director John Frankenheimer rushed a rough edit of the sequence to Frank Sinatra, then decided to keep the cut in the final movie unchanged.

On the copy of the New York Post announcing the slaying of Senator Jordan and his daughter, a small headline at the top reads: "VIOLENT HURRICANE SWEEPS MIDWEST; 20 DEAD, HUNDREDS HOMELESS"

One of the early uses of martial arts in a Hollywood film is a key fight sequence (between Frank Sinatra and Henry Silva), over a decade before the Kung Fu craze of the 1970s. Still earlier, however, is Blood on the Sun, with its climactic judo bout involving James Cagney. And though Peter Lorre was using jujitsu in Mr. Moto movies as early as 1937, Harry Parke (as Parkyakarkus) mentions jujitsu in the Eddie Cantor movie Strike Me Pink.

One scene was filmed at the Bar and Grill that Frank Sinatra's friend Jilly Rizzo owned in New York City.

Prior to the commissioning of the book as a movie, Arthur Krim, then President of United Artists and Finance Chairman of the Democratic Party, is known to have felt uneasy about its subject matter. President John F. Kennedy, as a favor to his friend Frank Sinatra, called Krim to let him know that he had no objection to a film version being made.

Rosie's number, ELdorado 5-xxxx was once a telephone company test number that would always give anyone who calls it a busy signal. However, as of 2009, the number is active in at least one area code.