The movie began filming in August 1979, but did not debut theatrically until 1981. (It was shown at the Cannes Film Market in May 1980).
Tatum O'Neal had to keep her legs covered throughout the entire movie, including during her topless scene. This is because she had been involved in a terrible car accident shortly before filming, and her legs had suffered second and third-degree burns from skidding on the pavement.
Richard Burton once said of this film: "'Circle of Two' is a delicately balanced story. The two personalities have to complement each other very much and be totally believable or they run the risk of being just a dirty old man with a beautiful young girl. It's a tremendous job for the director."
When Sarah Norton (Tatum O'Neal) goes to the porn theater where she meets Ashley St. Clair (Richard Burton) for the first time, Lee Majors and Tatum's father Ryan are clearly seen as two of the people in the theater. Ryan O'Neal visited the set often to supervise his daughter, due to the film's sensitive material.