Frederick Forsyth, who wrote the novel "The Day of the Jackal", insisted his name be taken off the credits of this film, which is why it is billed as "based on the screenplay".
After the filming of this movie, Bruce Willis and Richard Gere reportedly vowed to never work with each other again.
Because Richard Gere and Bruce Willis filmed many of their scenes separately, they would often ask each other "How's your movie going?" when they'd meet.
This isn't the first time Richard Gere was considered for a role that Bruce Willis got. The first was the role of John McClane in Die Hard (1988), which Gere turned down.
Before Bruce Willis was cast, Richard Gere was offered the role of The Jackal. He turned it down and instead asked if he could play the hero.