The cardiac electrical field is important not only because of its diagnostic significance, but also as a biological and biophysical phenomenon. As such, it has become a research target of biologists, biophysicists and biomathematicians. It has also been an impetus for constructing more and more sophisticated measuring devices. Criteria for the diagnostic evaluation of body surface potential maps have often been derived from clinical studies based on a restricted number of cases. Further clinical research is therefore a conditio sine qua non for the acceptance of mapping as a routine diagnostic procedure. In the future, body surface potential distributions will be used as the input for computer simulation of potential distribution and activation chronograms on the geometric surface closely encompassing the heart. In such a way, electrocardiographic signals will be interpreted in terms of activation and repolarization sequences on the cardiac surface.