A computer algorithm for 3-dimensional computer simulation of electric phenomena in the human heart has been completed, in which the heart model consists of 50,000 functional cells arranged in the cubic close-packed structure and various waveforms of the action potential have been allotted to these functional cells. The present model allows one to estimate time courses of ECG, VCG, and body surface potential distribution from the P-wave up to the T-wave. It also can simulate electric phenomena in the heart with anomalies in the conduction system and the myocardium.