Lovers and Other Strangers is a 1970 comedy film based on the play by Renée Taylor and Joseph Bologna. The cast includes Richard Castellano, Gig Young, Cloris Leachman, Anne Jackson, Beatrice Arthur, Bonnie Bedelia and, in her film debut, Diane Keaton. Sylvester Stallone was an extra in this movie.
The film was nominated for three Academy Awards (it won the Academy Award for Best Original Song), and was one of the top box office performers of 1970. It established Richard Castellano as a star (receiving an Oscar nomination for his performance) and he, along with Diane Keaton, was subsequently cast in The Godfather. The song For All We Know was composed by Fred Karlin with lyrics by Robb Royer and Jimmy Griffin.
Lovers and Other Strangers was released by ABC Pictures. It was released on VHS in 1980 by Magnetic Video, but soon went out of print. The Magnetic Video release was a collector’s item for many years, but the film was eventually re-released on VHS by CBS/Fox Video in the 1990s. It is now available on DVD by MGM Home Entertainment.
Summary via Wikipedia.