The Perceptual Computing Section of the Media Laboratory is working to make computers that understand people, and can work with them in the manner of an attentive human-like assistant. To this end we have built a series of interactive office spaces that are used as real-time experimental testbeds. These spaces are instrumented with cameras and microphones, and perform audio-visual interpretation of human users. Real-time capabilities include 3-D tracking of head, hands, and feet; ``holographic'' audio; face recognition; and interpretation of face and hand gestures. People in the space can control programs, browse multimedia information, and experience shared virtual environments without wires or special goggles.