There are many reports in which the ECG were exlained by the change of solid angle at point to lead subtended by the activated ventricular area, but no one has ever discussed the ECG measuring actually the solid angle at that point. Toyoshima and associate reported previously that ECG and VCG could be reconstructed from their results of potential calculation, when the ventricular activation process were known. So, I attempted the reconstruction of ECG and VCG by their method under various assumptive activation processes dividing them into eight stages. Since the potential calculation having been done only on epicardial surface of plaster model of human heart, the potential due to septal activation could not be obtained. But the effect of septal activation may not be large because of almost the same onset of septal activation in both side. The potential due to endocardial surface was assumed as one half of those due to the corresponding epicardial surface in the first depolarization stages. In the sequent stages, I assumed those potentials as 0.7 to 0.8 times of latter, and in the last stafe of subendocardial depolarization as the same with latter.The method of reconstruction of VCG and ECG. The potentials at the leading points by cube system method and polyography were obtained by calculation in each stage of depolarization. From these calculative potentials, the manifest vectors were reconstructed geometrically, and the VCG were recorded by plotting the ends of these vectors. Standard limb lead ECG were obtained from potential difference between the representative points of extremities. Unipolar lead ECGs were obtained by subtracting one third of the sum of three extremity potentials from their potentials.ECG and VCG thus obtained resembled closely to the usual ones, and the assumptive activation processes used for the reconstruction were not much differed from that by Lewis, by Harris and by Toyoshima. By this method, the relationship between the VCG or ECG and ventricular activation process of human heart could be ascertained more theoretically than usual methods, and the following facts could be also confirmed.1) It was desirable selecting the center of spatial vectorcardiographic reference system as near as possible to the cardiac center level, while the configuration of VCG was inscribed normally when the center of reference system was placed on the same level with cardiac center, and when it was displaced, the VCG was recorded in abnormal configuration. For example, when the leading points were selected higher as much as 10 cm than that, sagittal plane VCG was inscribed in contrary direction.2) Various electrical heart positions were found even from the same heart position, if the activation process were changed.3) Strictly speaking, unipolar precordial ECG were not scalar projection of horizontal plane QRS-loop of VCG in geometrical sense.4) The time of arrival of activation was marked at anywhere in the intrinsicoid deflection and not at the specific point of it.5) The typical configuration of the VCG and ECG of cor palmonale was obtained by increasing the area and delaying the activation stage of concerning heart region. It was suggested also that the ECG and spatial VCG of hypertrophy, bundle branch block, and myocardial infarction might be reconstructed in the same way.