Features the first depiction of female orgasm (sound only) to be passed by the British Board of Film Censors.
This film, along with Rosemary's Baby (1968) and Le locataire (1976), forms a loose trilogy by Roman Polanski about the horrors of apartment/city dwelling.
In his autobiography, Roman Polanski admitted that he and co-writer Gérard Brach came up with the film so as to have a commercial success which would then help them fund the making of Cul-de-sac (1966), a much more personal project for them.
After unsuccessfully pitching the film to Paramount Pictures and British Lion Films, director Roman Polanski and producer Gene Gutowski, eventually received financing from Compton Pictures, a small distribution company that had been known primarily for its distribution of softcore pornography films.
When Roman Polanski first announced this, he stated the actress he required would have to be "an angel with a slightly soiled halo".