This is a comparison between the cut BBFC 18 VHS released by MGM/UA and the uncut DVD releaed by Retrofilm.

There are 4 missing scenes with an overall runtime of 1 minute and 13 seconds.

This little horror movie about a group of young people, that make a small tour through Alcatraz and run into a demon had a pretty rough time regarding its international release. So far, the US received a cut R-Rated-Release. It is even possible that this version was shortened even further. The British BBFC 18 version had been cut as well. The VHS includes four cuts and is based on the R-Rated version. Thus far, there is no uncut release neither in the UK nor the USA.

2 min
The title is different in both versions.
BBFC 18-VHS: Hell Island
Uncut DVD: Slaughterhouse Rock.
No difference in time.

28 min
The demon slashes his sabre deep into Alex' body who is hanging above the fire. The demon rips a part of Alex' body out and puts it into his mouth.
6 sec

48 min
At frist, Richard rips his girlfriend's blouse open, after that he also takes her pants off. He opens his pants, pulls them down and starts raping Krista. She unsuccessfully tries to fight him off. Krista starts screaming when he transforms into the demon.
36 sec

48 min
Again you can see Richard raping his girlfriend. She screams and tries to grab something to hit it against Richard's head.
7 sec

52 min
The general cuts the native several times with his sabre. From off-screen, a woman comments that he became more and more perverted and formed the habit to take pleasure in torturing the natives. Then she says that he entirely lost it and solely ate human flesh. During the next scene we see him sitting on a chair and eating his dead wife's flesh. The woman's corpse is lying on the bed in front of him. The general turns around and looks into the camera. His eyes look fiendish.
24 sec