The fundamental purpose of this paper is to present the results of a feasibility study for an on-line, real-time automatic range gate tracker (ARGT) for clinical echocardiography, specifically for the purpose of determining cardiac output noninvasively and in real time. The basic ARGT design represents an implementation of specific algorithms and a system controller that permit user interaction and interpretation of clinical echocardiograms. In its analytical mode, the ARGT automatically tracks cardiac echoes as visually perceived and selected by the user. While tracking specific cardiac echoes, the ARGT converts the complex ultrasonic echogram into a pair of meaningful analogue signals (corresponding to the motion of the anterior and posterior left ventricular walls) from which dimensional information corresponding to dynamic geometric changes of the heart are derived. From the information, the cardiac output is computed in real time.