Abstract: Non intrusive human body tracking is a key issue in advanced human-computer interaction, with applications ranging from virtual reality to videoconference and telepresence. This paper describes a system for vision-based tracking of body posture. The system is explicitly designed to provide a robust yet simple and inexpensive solution to real-time body tracking through a careful choice of visual and kinematic models. Human posture representation is fully compatible with the MPEG-4 standard. Results of system application to a computer graphics scenario (animation of 3D avatars) are presented and discussed.