Abstract: A portable ranging system for analyzing gait is disclosed comprising a transponder having an infrared receiver and an ultrasound emitter, a base unit having an infrared emitter and an ultrasound receiver, and a computer terminal. During gait analysis, the transponder is worn by a subject at approximately the level of the body center of mass. As the subject walks away from the base unit, the base unit continuously causes, at a constant sampling rate, the ultrasound emitter to emit ultrasound pulses. These ultrasound pulses are received by the ultrasound receiver of the base unit. The computer terminal, by counting during the flight of each ultrasound pulse, is able to calculate the time of flight of each ultrasound pulse, and thus calculate and display in real time the forward progression of the subject. At the end of the walking trial, the computer terminal displays the instantaneous velocity profile, or gait velocigram (GVG), for that trial.