Body Surface Potential Mapping (BSPM) is a new tool in electrocardiography for imaging cardiac potentials measured at the torso skin, and potentially for imaging epicardial potentials, BSPM can be used to localize electrical foci in the heart as in WPW syndrome, infarction, or normal conduction, but the technology for a practical BSPM system is just now available. Our objective is a stand-alone portable BSPM system requiring minimal operator assistance in acquiring data from 180 electrodes, producing images of potentials on the torso skin, extracting features of the image sequences in a report to clinicians, and providing some analysis of those features as an aid to the clinician. In Phase I, we will concentrate on the remaining hardware and software problems in data acquisition, so that good quality data can be recorded from patients from infants to adults. In Phase II, emphasis will shift to research on processing and analyzing the potential data as a three dimensional set of values, where information is encoded in the three dimensional features. With a safe reliable system for efficient acquisition (Phase I), and analytical software (Phase II), a commercial instrument should emerge.