A probabilistic framework for vision based volumetric reconstruction and marker free tracking of hand and face volumes is presented, which exclusively relies on off-the-shelf hardware components and can be applied in standard office environments. Here a 3D reconstruction of the interaction environment (user-space) is derived from multiple camera viewpoints which serve as input sources for mixture particle filtering to infer position estimates of hand and face volumes. The system implementation utilizes graphics hardware to comply with real-time constraints on a single desktop computer. Key words: Probabilistic Shape From Silhouette, Mixture Particle Filtering