According to the DVD documentary, the first cut of the film had a longer "Visions from Hell" sequence, more blood, and a different, though similar, ending. The test audience didn't like it, so it was re-cut with an alternate ending involving what director Paul W.S. Anderson called "The Burning Man Sequence." The second test audience didn't like that version, and the film was edited again. The final cut is a less-intense hybrid of both test screenings, with significantly less gore.
Director Paul W.S. Anderson and producer Jeremy Bolt planned to put together a director's cut for some time, but most of the footage was lost or destroyed after post-production. A few of those scenes, which appear on the Special Collector's Edition DVD, survived only in videotape form, sometimes without dialog or sound effects. The DVD also includes storyboards of a space walk sequence that was abandoned for budget reasons, and the alternate ending, with commentary by Paul W.S. Anderson.
According to the DVD commentary, sequences deleted from the "Visions of Hell" include orgies and sadomasochism killing the Event Horizon's original crew.
Paul W.S. Anderson's initial cut of the film ran to 130 minutes and was quite graphically violent, so much so that both test audiences and the studio baulked at the finished product. Paramount ordered him to cut the film by 30 minutes and tone down some of the violence, a decision he now regrets.
Some of the lost footage includes a great deal more of the Bosch-influenced Hell sequences and of the orgiastic video log that was found in the Event Horizon. This was shot by both director Paul W.S. Anderson and Vadim Jean, mainly on weekends.