An American Werewolf in London is perhaps one of the most famous werewolf movies ever made, and revolutionized the special effects used in the sub-genre, which had been using basic cross dissolves and makeup changes since the The Werewolf of London in 1935. However, one scene dealing with special effects was lost after test audiences reacted negatively to it.
There is no know visuals or audio from the scene, and no detailed descriptions of what happened in it. All that is known is that it was death scene for the tramps. In the current version of the movie, the movie simply cuts to another scene where the lost death scene was. As there are no decent views of the tramps when they appear as ghosts in the theater later in the film, there is no knowing how they died.
Much like the spider pit scene in the original King Kong, the sequence distracted the audience from other, more vital parts of the film, and was cut before the final release. It is believed that nothing is left of the scene, and it is unlikely it will ever be found.
Worth noting was other, smaller cuts made in other countries. In America, the sex scene was shortened and shots of food falling out of Jack's mouth when he eats toast were removed. Other countries removed the scene where David calls home to his sister before trying to slit his wrist with a pen knife. On TV, the climatic werewolf rampage is often heavily cut down to remove most of the graphic violence. There is an unrated cut of the movie which has more blood and gore, but is exceptionally rare and does not have the cut scene.
The making of and detailing some of the editing in the movie , retrieved Sept 23, 2009