William Hurt wanted to play the role of Paul Maclean and once went fishing with Norman Maclean in Montana. When Hurt asked if he had fished well enough to portray his brother, Maclean replied: "Well, Bill, you're a pretty good fisherman but not good enough to be my brother.".
Norman Maclean often recounted the story of how his semi-autobiographical story collection was rejected by every large commercial publisher he sent it to, including one that rejected it on the basis that it contained "too many trees". It was eventually published instead by the University of Chicago Press (in 1976) and went on to sell extraordinarily well for them.
George Coonenbergs was a retired railroad engineer. He taught Brad Pitt, Craig Sheffer and Tom Skerritt how to fly-fish for this movie. He also taught fly-fishing and fly-tying to his fellow residents, and staff members, of his retirement community. He grew up near the Maclean family in Missoula, Montana. His family's cabin was built next door to the Maclean family cabin in Seeley Lake, Montana. He learned to fly-fish and tie flies from Rev. John Maclean, and was considered Paul Maclean to be his best friend. The friendship between the Maclean and Coonenbergs families continues to this day, into its fourth generation.
Even though the film claims that it is filmed in Missoula, it is actually filmed in and around Livingston, Bozeman and Big Timber, Montana. Many of the fishing scenes were filmed in the Gallatin Canyon on the Gallatin River south of Bozeman.
Trout used in the movie were pond-raised in Montana and were kept in a specially aerated and cooled tank truck until their big moment in front of the cameras. No hooks were used, and no blood was drawn. A line was tied to each fish's lower jaw under the careful observance of the Montana Humane Society.
Brad Pitt auditioned twice for the role of Paul Maclean. The first time he thought that his performance was really terrible, so he insisted in sending a tape performing another scene and that scene convinced the director that Pitt was the perfect choice.
The film was originally produced by Carolco, the studio responsible for Terminator 2: Judgment Day (1991) and the Rambo films, among others. Due to the serious debt Carolco was facing, Robert Redford called upon film producer Jake Eberts to put in the financing of the pre-production. During post-production, Carolco sold their rights to the film to Eberts.
The bottle of whiskey served to Paul and Ol' Rawhide in Black Jack's bars has the numbers 3-7-77 on the bottle. 3-7-77 was the symbol used by the Montana Vigilantes (Vigilance Committee) in Virginia City, Montana. People who found the numbers '3-7-77' painted on their tent or cabin knew that they had better leave the area or expect to be on the receiving end of vigilante justice.
Elmer Bernstein wrote the original score for this film. However, it was rejected by director Robert Redford, so Mark Isham composed a new one (for which he received an Oscar nomination). In the original theatrical version of the film, Isham was credited as the composer during the opening credits. But for some reason, in some video and DVD versions of the film, Bernstein is credited as the composer.