In biomechanics research and in many sports medicine applications, it is desirable to make precise measurements of the kinematic parameters of body motions. An analysis of these parameters can be used to refine athletic performance, to design sports equipment, to develop orthotics, and to improve the practice of sports medicine. In this paper a videometric analysis system is described that can meet the requirements of a broad range of clinical and research applications. This system consists of state-of-the-art video components, including a shuttered video camera and a high resolution electronic cursor system, as well as a microcomputer and appropriate software for interactively making measurements, displaying results and producing reports. The use of this system for making gait measurements of athletes running on a treadmill is described. Time series of rearfoot angle measurements, made during the support phase of a gait are produced by the system. Individual gaits can be analyzed, or a number of gaits from one or more athletes can be grouped for statistical evaluation. An archival storage and retrieval facility permits the development and use of an extensive data base.