The body-surface map provides an integral picture containing more information on the activation sequence of the heart than is available from a standard 12-lead electrocardiogram (ECG) or vectorcardiogram (VCG), because the body-surface map has a larger number of lead points that the ECG, and they are uniformly distributed over the entire thorax and back. It supplies instant-by-instant information about the distribution of the positive and negative potential areas over the body surface. Therefore, body-surface mapping is a very powerful diagnostic tool for assessing the activation sequence of the heart and is likely to play an important role in determining the focus of various arrhythmias and the site of bypass tract and also clarifying the physiological mechanism of arrhythmias.