When Jane Fonda asked her father for advice on what to say for her Oscar acceptance speech, he suggested: "There's a great deal to say, but I'm not going to say it tonight."
Although Fonda had planned on playing scared for the scene with the murderer (played by Charles Cioffi), when she heard the tape recording of the call girl about to be murdered and the fear in her voice, she unexpectedly started crying.
When Bree and Klute return to Bree's apartment from the market, the phone rings. Klute lifts the receiver halfway through the third ring whereupon the sound of the bell abruptly cuts off (rather than resonate a couple of seconds as it did during the first two rings), revealing the phone's ring as a studio recording.