Trivia

An envelope is dropped on the desk of Eliot Ness in one scene. It is assumed to be a bribe, but the amount inside is never revealed. In real life, Al Capone promised Eliot Ness that two $1,000 bills would be on his desk every Monday morning if he turned a blind eye to his bootlegging activities (an enormous amount of money then; more than $30,000 today). Ness refused the bribe, and in later years struggled with money. He died almost broke at the age of fifty-four.

In real life, Al Capone, knowing that killing a Prohibition agent would only lead to more trouble than he or his outfit could handle, actually had a non-violence order to his men concerning the Untouchables. While Capone did repeatedly attempt to buy them off, he never once attempted to kill Eliot Ness or any of his men.

Albert H. Wolff, the last survivor of the real-life Untouchables, was a consultant on this movie, and helped Kevin Costner with his portrayal of Eliot Ness.

Robert De Niro tracked down Al Capone's original tailors and had them make him some identical clothing for the movie.

According to director Brian De Palma and producer Art Linson in the DVD documentary, it was Sir Sean Connery's idea to film the "blood oath" scene between Ness and Malone in a Catholic church. Originally, it was going to take place on the street (in the same scene that follows the church scene). Connery felt that a church would be the only "safe" place in Chicago where the two characters would make such a commitment to fight Capone.

Brian De Palma: [filming technique] The close-up of Malone and Ness in the blood oath scene was shot using a split focus diopter. This is a half convex glass in front of the actual lens to make one half nearsighted and the other farsighted. The result is foreground and background (here both actors) are in focus. The effect can only be achieved when there is nearly no actors nor camera movement, and is often used to create more mystery. Brian De Palma has used this in many of his movies.