Angie Dickinson said the scene where her character gets seduced in the back of a taxicab was filmed on-location in New York City, where several gawkers observed the scene and shouted, "Right on, Police Woman!" (referring to her previous television role as the title character on Police Woman (1974)).
As a young man, at his mother's urging, Brian De Palma followed his father and used recording equipment to try catching him with another woman. That incident inspired this movie.
Angie Dickinson, Nancy Allen, and Keith Gordon all praised Sir Michael Caine's generosity and professionalism as an actor on this film. As the main star, he was only ever required to be on set when his character was in shot, but all three stated he insisted on also being there when his character was not in shot, so that his co-stars were always performing to his character and not to a stand-in or nothing at all.
This movie was originally rated X by the MPAA. Writer and director Brian De Palma fought the rating, and with editing eventually they brought this down to an R which greatly improved the film's chances of financial success.
Writer and director Brian De Palma specifically wrote the role of Liz Blake for his wife Nancy Allen to play. She was the first and only actress to whom he offered her role.