The analysis of human motion can be advanced by analyzing motion, not only numerically, but also graphically. We present a system for the three-dimensional graphical analysis of human motion. The system involves the integrated operation of an image acquisition unit, a robot arm for 3-D target presentation, an image reconstruction unit, graphic analysis, and animation software. A five degree of freedom robot arm is used to present single targets or target trajectories for subjects to track. All the locations are software generated based on mathematical formulation of the desired sectoring of space. Two optoelectronic cameras are used to directly sense the positions of the diodes. Three-dimensional trajectories of each point are computed from the two sets of 2-D images. The 3-D trajectories of the robot and of the subject are reconstructed and displayed on a Silicon Graphics Iris Workstation. A variety of programs display kinematic features of the hand and joint trajectories synchronized with reconstructed images of the three-dimensional trajectory paths of individual limb segments. The user has real-time interactive control over the viewing angle, size, and screen position of the limb trajectories. Image representing all 3-D target and finger positions and scatterplots of target and finger distance, azimuth, and elevation from the shoulder can also be presented. Finally, software was developed to display the reconstructed motion of the arm by representing the various segments of the arm as surfaced cylinders. Effects of light source, shading and shadowing are used for calculations of brightness over the surface of the various cylinders. The end points of each cylinder are determined by the 3-D locations of infrared diodes which were attached to the subject's limb segments. The arm is animated to reproduce the velocity patterns inherent in the digital trajectory records. There are various interactive options for viewing the moving image of the arm together with representations of the trajectories of the individual joints.