Abstract: An optimal electrophysiologic mapping system for map-directed arrhythmia surgery and cardiac research allows rapid and accurate interpretation of cardiac activation sequences. The system can display activation or potential distribution data on an anatomically accurate 3-D model of the heart and allows fast, interactive control of viewing characteristics, including control of which cardiac surfaces are displayed, control of virtual lighting, rotational control of the displayed image, etc. The system employs two computer programs, GETPIC3 and MAP3, and runs on a Silicon Graphics workstation capable of rapid graphics calculations and displays. The system utilizes 3-D models of epicardial and endocardial surfaces created with the GETPIC3 program from a sequence of 2-D images of a heart. The individual surfaces are triangulated and may be smoothed using a spline function. The MAP3 program displays activation times either as static isochronous maps or as dynamic time-since-last-activation maps.