- The film was shot at director Lindsay Anderson's actual old school in Cheltenham, as well as Aldenham School, England.
- Contrary to the story that says some scenes of the film are in BandW instead of color because the production company was running short of money and saved money by having some scenes processed in monochrome, according to interviews with Malcolm McDowell, Lindsay Anderson and the cameraman, they first shot the scenes in the school chapel in monochrome because they had to use natural light that came in through the big stained-glass window, requiring high-speed film. The high-speed color stock they tested was very grainy and the constantly-shifting color values due to the angle of the light through the stained glass made it impossible to color-correct, as well. So they decided to shoot those scenes in monochrome, and, when he saw the dailies, Anderson liked the way that it "broke up the surface of the film", and decided to insert other monochrome scenes more or less at random, to help disorient the viewer as the film slipped from realism to fantasy.
- Malcolm McDowell's film debut.
- The first film of Simon Ward.
- Features the first instance of a full-frontal female nude passed by the British Board of Film Classification. Previously there had been instances of flashes of nakedness - notably in Michelangelo Antonioni's Blowup (1966) - but "If..." had a prolonged shot of featured nudity.
- In order for the full-frontal nude scene of Mrs Kemp to be passed in the UK chief censor John Trevelyan asked Lindsay Anderson to remove shots of male genitals in the shower scene. Anderson agreed to this and the film was released uncut with an X certificate. For its 1971 cinema re-release a 'AA' (no under 14) certificate was given after some trims to nudity during the coffee shop sex scene, though all later 15-rated video and DVD releases have featured the original uncut cinema print.
- The painting in the dining hall is Richard Platt from Aldenham School. The Hall scene was an amalgamation of the school halls at Cheltenham and Aldenham.
- The Packhorse Cafe doesn't exist anymore. It was on the Tewkesbury Road about four miles outside Cheltenham. The road in the film is lined with Elm trees and most of them vanished in the mid-70s because of an outbreak of Dutch elm disease, they've been replaced by another type of tree.
- Although the film was shot at Cheltenham Boys' College, the script "Crusaders" was based on the authors' old school Tonbridge School. Tonbridge was the original choice for the outdoor shots, but the school declined believing it would bring bad publicity. All-boys boarding schools were receiving quite unfavourable press at the time, which might explain Tonbridge's decision.
- The title of the film was suggested by the secretary of Memorial Films when she overheard Lindsay Anderson and David Sherwin endlessly debating possible titles.
- Rupert Webster was dubbed by Robert Langley.
- The motorcycle stolen by Mick is a 1968 BSA A65L Lightning (654cc parallel twin).
- The final shot actually repeats the same short bit of action backward and forward several times (smoke can be seen rising and then going back down, for instance) before finally going to a freeze frame
- Based on Jean Vigo's short film, Zéro de conduite: Jeunes diables au collège (1933)
- The driver of the red car stopped by Mick on the roundabout in Cheltenham was Michael Medwin, the film's producer.
- Widely regarded as one of the films that captured the great counterculture movement of the late 60s, shooting actually began several months before one of the most significant events of that movement - the student riots in Paris in May 1968.
- One of the provisions that Paramount made about the film was that it should be shot in a UK studio with a wholly British cast and crew. To keep costs down, Lindsay Anderson largely recruited from the theatrical world.
- The scene of the beating in the gym was completely adlibbed.
- A British ambassador called the film "an insult to the nation". The then Lord Brabourne read an early draft and called it "the most evil and perverted script I've ever read. It must never see the light of day".
- Paramount hated the film when they saw it and tried to dump it from cinemas. However, one of their tentpole films, Barbarella (1968), turned out to be a spectacular flop so they needed to replace it in cinemas with something else. Reluctantly, they wheeled out "If..." and were astonished to see it turn into a big critical and commercial success.
- The jukebox in The Packhorse Cafe is a 1958 Rock-Ola 1464 Music Vendor which was the first ever wall mounted jukebox, although here it is seen as a floor standing version. Unfortunately it is not clear which selection number plays "Sanctus".
- Malcolm McDowell was reportedly paid £90 a week for this role.
- Malcolm McDowell, David Wood, Richard Warwick, Robert Swann and Christine Noonan all receive "introducing" credits
- The female nude whose magazine picture Mick and his friends admire early in the film is Angela Dorian (aka Victoria Vetri) in her Playmate of the Year pictorial from the May 1968 issue of Playboy magazine.
- The shot where Mick and the Girl are seen rolling on the café floor naked when making love was Malcolm McDowell's idea (because he wanted to see his attractive co-star, Christine Noonan, for whom he admitted having a crush, in the nude.) However, when Lindsay Anderson accepted his star's suggestion, the director required McDowell to ask Noonan if she was willing to do so. (Her reply, according to McDowell, was "I don't mind.")
>>> WARNING: Here Be Spoilers <<<
Trivia items below here contain information that may give away important plot points. You may not want to read any further if you've not already seen this title.
- SPOILER: The filmmakers sent the school a fake script omitting the students turning on the staff and parents with guns.
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