Continuity mistake: When Curly Bill is shooting up the town while drunk, he fires about 10 more rounds than his six shooter can hold without reloading, and still has a round remaining when he shoots Marshal Fred White. In the 1880 court hearing held after Marshal White's death, Curly Bill still had 5 rounds remaining in his pistol.
Revealing mistake: When Wyatt Earp and the actress, whom he marries later in the movie, meet on horseback, they go on a fast paced ride that concludes after going down a steep hill. If you look at the actress' feet, you will see she is riding side-saddle - a very difficult feat considering the riding they do. If you look closely you can see her real leg, safely on the other side of the horse. The side-saddle leg must be fake.
Trivia: Val Kilmer has been quoted as saying that screenwriter Kevin Jarre insisted the actors wear real wool costumes, in accordance with the time period. During the scene in the Birdcage Theater, Val Kilmer says, a thermometer was placed on the set, and it read 134 degrees Fahrenheit. Kilmer suggested jokingly that this was the reason Doc Holliday killed so many people: "It's just, like, he wore wool in the summer, in the Arizona territory, and that made him mad."
Trivia: During filming Val Kilmer and Kurt Russell became good friends. One bought a grave slot in the actual Tombstone for the other and the other bought a piece of property in the town for the other. The fun thing is that neither knew that the other had bought them anything until they exchanged "gifts".