- Early choices for the role of Mark included Dirk Bogarde and Laurence Harvey.
- The cameras in Mark Lewis' room include director Michael Powell's first film camera, a hand operated Eyemo, made by Bell and Howell, that he won in a competition.
- Director Cameo: [Michael Powell] Peeping Tom's father, seen in an old home movie he shows the girl.
- In Mark Lewis' "home movies," Prof. A.N. Lewis is played by director Michael Powell, young Mark Lewis is played by Powell's real-life son, Columba Powell, and Mark's mother, seen lying lifelessly in bed, is played by Columba's real-life mother, Frankie Reidy.
- Premiere voted this movie as one of "The 25 Most Dangerous Movies".
- The character of Don Jarvis the studio boss is a parody of notorious Rank mogul John Davis.
>>> 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 film was heavily cut by the BBFC before release and consequently many scenes still have a ragged feel to them. The murders of Vivian and Dora were toned down, shots of nudity were deleted (including photos of nude girls in the album), the suicide of the killer was shortened, and scenes featuring the spike were also edited. Some dialogue was also cut (which explains the abrupt ending to the conversation between the policemen in the car). Although some cuts were restored in later video and DVD releases much of the edited footage is now considered lost forever.
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