Cristina Raines has said that the film crew actually used the exterior and the interiors of the Brooklyn Heights brownstone for the film. Raines says a lot of strange things happened while they were shooting there, particularly when she was assigned an apartment to use as her dressing room and found out it was being rented by a priest.
There are 2 different versions of the movie.
The "uncut" one on DVD and BRD feature catholic church, nudity and gore. The "censored" one for TV has all the church parts deleted and replaced by the "brotherhood of the sentinels".
The nudity, gore and dream scenes have been deleted almost to the point of harming the understanding of the plot. Some stuff have been added though on the rare and unreleased censored version: random devil pictures, a devil ring, a chronology of the sentinels and the police scene "it was suicide". This version was only available on cable TV.
The "uncut" one on DVD and BRD feature catholic church, nudity and gore. The "censored" one for TV has all the church parts deleted and replaced by the "brotherhood of the sentinels".
The nudity, gore and dream scenes have been deleted almost to the point of harming the understanding of the plot. Some stuff have been added though on the rare and unreleased censored version: random devil pictures, a devil ring, a chronology of the sentinels and the police scene "it was suicide". This version was only available on cable TV.
The modern apartment building at the end of the film was a visual effect; the original building still stands today.
Michael Winner claims the producer wanted Chris Sarandon because he was nominated for an Oscar for Dog Day Afternoon. Winner did not want Sarandon but was afraid to confront the producer. A few weeks into shooting, Winner claims the producer saw dailies with Sarandon and asked "What the hell is this Greek waiter doing in my film?!?" (Referring to Sarandon). Winner told him that was the actor he asked for and by that time no change could be made.
Richard Dreyfuss: (at around 7 mins) Man talking to girl in red sweater as Cristina Raines and Deborah Raffin are walking on the sidewalk.