• The costuming is wrong for the time period, especially the hat styles, according to historian Jeff Morey.  Only Doc Holliday wears the right kind of hat.  The movie Tombstone is much more accurate in that regard.
• The Oriental Saloon, a central location in the film, appears on the wrong side of the street.  The real Oriental was on the northeast corner of Allen and Fifth streets.
• Curly Bill is shown shooting Marshal Fred White deliberately.  In reality, the shooting was accidental.  Marshal White said so himself.
• As in Tombstone, Fred White is portrayed as an older man.  He was, in fact, only 31 when he was killed.
• Wyatt Earp has Virgil and Morgan Earp shot on the same night, shortly after the "OK Corral" street fight, as they are in the movie Tombstone.  The truth is that Virgil was shot on December 28, 1881, two months after the fight, and Morgan was killed on March 18, 1882, nearly five months after the fight.
• In reality, Virgil was shot in (and lost the use of) his left arm.  The movie has him shot in the right arm.
• John Ringo was not killed during Wyatt's shootout with Curly Bill.  In all likelihood, Ringo wasn't even there.  Ringo was found dead on July 14, 1882, of a suspected, but univestigated, suicide.
  
• The reference to Tommy-Behind-The-Deuce near the end of the film is a deliberate misnomer of Johnny-Behind-The-Deuce, a real character in the Wyatt Earp saga.  It's been said that the name was changed to Tommy because too many other men are named Johnny in the movie, as in Johnny Behan, Johnny Ringo, Johnny Tyler and John Clum (who were all real people).

A larger list of Wyatt Earp inaccuracies can be found on this Wikipedia page.