The producer chose to change the ending, and both Curtis Harrington and Piper Laurie refused to be involved in the re-shoot. It was allegedly shot by Stephanie Rothman, who has neither confirmed nor denied her involvement. This ending, featured in the TV commercials at the time of the theatrical release, helped make it the box office success it was.
This horror movie was reportedly the highest grossing independent film prior to Halloween (1978) which was first released the following year.
The version broadcast on television contained a lot of footage not seen in the theatrical version. The footage was allegedly shot by Stephanie Rothman, new for the TV sale, not scenes deleted from the original version. This version was also available on VHS tape. The DVD release is the theatrical version.
According to both actress Piper Laurie and director Curtis Harrington, legendary German filmmaker Leni Riefenstahl admired this film.
The producers wanted actress Tina Louise for the title role before the name of actress Piper Laurie was mentioned.