There are two versions generally available, the R-rated theatrical cut and the Unrated Director's cut. Differences in time is about 4-5 minutes (1h 33m (93 min) versus 1h 37m (97 min--director's cut)). Content wise, the Director's cut tends to be bloodier and more explicit in its depiction of violence. It also makes clearer that zombies can be created by a person's death as well as by an infecting bite.