First person games are computer games, in which the user experiences the virtual game world from an avatar’s view. This avatar is the user’s alter ego in the game. In this paper, we present a telepresence interface for the first person game Quake III Arena, which gives the user the impression of presence in the game and thus leads to identification with his avatar. This is achieved by tracking the user’s motion and using this motion data as control input for the avatar. As the user is wearing a head-mounted display and he perceives his actions affecting the virtual environment, he fully immerses into the target environment. Without further processing of the user’s motion data, the virtual environment would be limited to the size of the user’s real environment, which is not desirable. The use of Motion Compression, however, allows exploring an arbitrarily large virtual environment while the user is actually moving in an environment of limited size.