The film was shot at the Spahn Movie Ranch in Simi Valley, CA, at the same time that Charles Manson and his "family" was living there. In fact, this was exploited in the film's advertising with the line "Filmed in the exact location that the Tate hippie killers lived their wild experiences!"
Generally thought to be the first film to feature someone being killed by having their head shoved down a toilet bowl.
The red tinted sunglasses that Russ Tamblyn wears in the film were his own idea, and his floppy hat was a carryover from his previous film, Scream Free! (1969).