The concept of the ventricular gradient proposed by WILSON et al. have been taken into account as an important parameter in the differentiation of the primary change of ST-T from the secondary one. Normal spatial ventricular gradient were derived from the component ECG of the Frank system, one of the corrected orthogonal leads. Three component leads (X, Y, and Z lead) of the vectorcardiograms of the Frank system were recorded simultaneously with paper speed of 100mm per second. 110 healthy individuals aged 18 to 30 and 100 healthy individuals aged 31 to 50 were subjected to the study. The standardization were adjusted so that a 1mV gives a 10mm upright deflection. The original X, Y, and Z ECG were taken on film and were printed out in a magnification of three diameters. The enlarged curves of QRS and T waves were traced along their uppermargines with a planimeter, excluding Ta wave followed up using the method of BERKUM et al. And the time of the onset of QRS wave, the end of QRS and T wave were determined using of the simultaneous X, Y, and Z leads. The u-p segment was adopted as the isoelectric baseline. The analytico-geometrical computation were carried out for the following parameters using the digital computer, OKITAC 5090-H type, Kyushu University Computation Center: the spatial ventricular gradient (SA^^^VG), the spatial QRS area vector (SA^^^QRS), and the spatial T area vector (SA^^^T). Mean value and range were deter-mined for the following items: azimuth (H), elevation (V), and spatial magnitude (Mag.) of SA^^^VG, SA^^^QRS, and SA^^^T, their angles and magnitudes projected on the perpendicular planes, spatial angle between SA^^^QRS and SA^^^T (dA), spatial angle between SA^^^QRS and SA^^^VG (dB), spatial angle between SA^^^VG and SA^^^T (dC), ratio of the spatial magnitudes between SA^^^VG and SA^^^QRS (SA^^^VG/SA^^^QRS ratio), and ratio between SA^^^T and SA^^^QRS (SA^^^T/SA^^^QRS ratio). All the magnitudes are then expressed by microvolt second, and directions by degree. Stature, weight, and chest circumference of the subjects are shown in the Table I. Spatial ventricular gradients and the related vectors in normal young men are given in the Tables II-IV. Mean values of SA^^^VG-Mag., SA^^^VG-H, and SA^^^VG-V were 127 ± 39.6 (56.0 - 208.7) μVsec, 16.0 ± 11.0 (71.0 - -2.0) degrees, and 46.9 ± l0.9 (75.0 - 19.5) degrees, respectively.