The infuluence of 2 stout build on the body surface electrocardiogram was studied by comparing the body surface isopotential maps of 93 normal men and 107 obese men without cardiovascular abnormalities. There were no clear differences in the mean map patterns between these groups, although the position of the peak maximum positive potential shifted slightly leftward in the obese group. The maximum positive potentials of the QRS wave (Rmax V) and T wave (Tmax V) at 87 lead points on the left anterior chest and back surface were significantly greater in the obese group. However, on the lower anterior chest surface, the values of Rmax V were smaller in the obese group. The correlations between the Rmax V of the lead points where significant differences between the groups were found and the relative body weight, skinfold thickness, chest configuration, mean frontal QRS axis of ECG, age and respiratory function ( % VC, FEV 1.0%) were studied statistically. There were good correlations between Rmax V and the QRS axis and relative body weight. However, there were no apparent correlations between Rmax V and the chest configuration and skinfold thickness. These results suggest that obesity might lead to an increase in abdominal grith and elevation of the diaphragma that produces a mechanical effect on the heart, causing a left-axis shift.