Using the FRANK and the TAKAYASU lead systems, 102 clinically and electrocardiographically normal subjects and 10S subjects with left ventricvlar hypertrophy were each quantitated in a series of thirteen instantaneous vectors both in the depolarization and the repolarization phases. Eight instantaneous vectors were determined at time intervals of 0.01 second from the beginning of the QRS complex. While in the QTC Vectors, five instantaneous vectors were fixed at time intervals of 0.01 second from the beginning of the Q wave and normalized in time by the formula of TAKAHASHI²0 Significant observations in this study were as follows : (1) Both planer and spatial QRS-T angles in left ventricular hypertrophy had wider or larger mean values than in the normal. The T/QRS ratio in the LVH group was significantly smaller than in the normal. (2) In spatial amplitude and orientation in the depolarization phase in the present series, the 0.04 sec QRS vector served to separate the normal from left ventricular hypertrophy by comparing the vectors preceding and following this prominent vector (0.04 sec QRS vector). (3) Also in the repolarization phase, the 0.30 sec QTC Vector served to separate the normal from the LVH, by comparing the preceding and the following vectors of the 0.30 QTC vector. (4) Between the two orthogonal lead systems, the FRANK and the TAKAYASU, there was no remarkable difference in the spatial orientation (azimuth and elevation) in the series of the instantaneous vectors. But, in magnitude, the latter lead system showed larger values, and this was advantageous for analyzing the smaller loops and the zero point of the vectorcardiogram.