Sutherland and Fonda developed a nonexclusive romantic relationship offscreen which lasted until about June 1972. He was her date to the Oscars when she won Best Actress for this movie.
The scene with the psychiatrist was mostly ad-libbed. Pakula used just one camera and later said he should have used two, as Vivian Nathan's reactions were much more interesting in the takes where the camera focused on Jane Fonda.
The first installment of what informally came to be known as Pakula's "paranoia trilogy." The other two films in the trilogy are The Parallax View (1974) and Đoàn Tùy Tùng Tổng Thống (1976).
In the original script, Bree's psychiatrist was male, but Fonda felt in rehearsals that the character would never open up to a man, and so she requested that the part be changed to a woman. Fonda requested to shoot the scenes with the psychiatrist at the end of shooting so that she would have already fully internalized the character of Bree.
Future film star Sylvester Stallone made an appearance as an extra in this film. He's the one dancing in front of the organ pipes during the first disco scene.