The haunting flashbacks that Ben Rolf has about the creepy chauffeur were based on an actual childhood experience of Dan Curtis. Curtis recalled as a young child being at his mother's funeral and seeing a chauffeur laughing outside of the funeral parlor which disturbed him deeply. He wrote the memory into the film, and the chauffeur became a most eerie character.
In the commentary with director Dan Curtis, he says that he actually read the novel 'Burnt Offerings' years before he got the offer to direct this film. Curtis said that he hated the open-ended conclusion of the novel and, at the time, thought to himself that he would pity anyone who would attempt to make it into a movie. Ironically, years later, the offer to direct the movie version of the novel came to him, and the first thing he did was write an ending that he liked - the one featured in the film.
The shot where the vines seize Oliver Reed's legs during the escape attempt were actually done in reverse. The vines were originally unwrapped from the legs and dragged off, but in reverse the vines appear to grab his legs.
In his DVD commentary, director Dan Curtis explains that he dropped an entire 15-minute opening with the family in New York, seeing the ad about the house for rent in the paper and Ben getting a parking ticket, because it was "boring".
According to "All His Jazz, The Life and Death of Bob Fosse," by Martin Gottfried (1990; Da Capo Press, 1998), David Begelman of CMA suggested "Burnt Offerings" to Fosse as a project after he completed Sweet Charity (1969), but before it was released. The author of "Burnt Offerings," Robert Marasco, had recently written a successful Broadway thriller, Child's Play." Fosse worked on a script and "spent three months preparing (it), working out a budget and scouting locations with designer Tony Walton, but the project ultimately fizzled." It was to be produced by Lawrence Turman, who had produced The Graduate (1967), but Fosse's friend, director Stanley Donen, thought it was a bad idea. "Don't do it!" he pleaded. "It's no damned good. Why are you doing it?"
The trivia item below may give away important plot points.
While shooting the film's finale, where Ben flies out the attic window and falls, the film's stuntman had a near-disastrous accident. He projected himself too far out from the window, and the crew waiting below had seconds to move the safety padding for his landing. The stunt man almost missed the padding, landing a mere foot or so from the end of it.