Alan Alda said what inspired the film was an actual incident where he judged a friend too harshly. He realized that not only was he wrong, that friendship goes through "seasons"; so he wrote the script based on that notion.
The scene where Jack (Alan Alda) calls Kate (Carol Burnett) "perfect" was not in the original script. Burnett asked for the scene to be added.
This film was the ninth most popular movie at the U.S.A. and Canada box-office in 1981.
The ski scenes were filmed in New England during a very dry winter. In fact, the only snow the ski resort got that entire season happened just days before the crew arrived to film.