In order to find a sensitive electrode position and to examine the criteria for the diagnosis of LVH, discriminant analysis was applied to body surface isopotential maps recorded by Yamada's method. The subjects consisted of 35 patients with hypertension, 25 with aortic regurgitation, 20 with hypertrophic cardiomyopathy and 45 normal controls. The subjects were divided into two groups, those with and those without LVH, according to the echocardiographically- obtained LV mass calculated by Devereux's method. Using discriminant analysis, we investigated the S and R waves to verify which position was the most sensitive for the diagnosis of LVH. The amplitude of the S wave was examined at 28 points from the right midclavicular line to the left midclavicular line including V(1)-V(3), and the amplitude of the R wave was examined at 33 points from the left midclavicular line to the left scapular line including V(4)-V(6). The sensitive positions were: for the S wave, the right sternal border in the third intercostal space (D5), and for the R wave, the fourth intercostal space along the left midaxillary line (I-4). Lead D5 was to the right and above V(1), and lead I-4 was abobe V(6). The diagnostic criteria of LVH indicates high sensitivity (82.5%), high specificity (87.5%) and high accuracy (85.0%), and is better than the Sokolow-Lyon's criteria, SV(1)+RV(6)≧3.5mV.