Abstract. This paper describes the development of a real-time perceptive user interface. Two cameras are used to detect a user’s head, eyes, hand, fingers and gestures. These cues are interpreted to control a user interface on a large screen. The result is a fully functional integrated system that processes roughly 7.5 frames per second on a Pentium IV system. The calibration of this setup is carried out through a few simple and intuitive routines, making the system adaptive and accessible to non-expert users. The minimal hardware requirements are two web-cams and a computer. The paper will describe how the user is observed (head, eye, hand and finger detection, gesture recognition), the 3D geometry involved, and the calibration steps necessary to set up the system.