The purpose of this study was to compare body surface isopotential maps with echocardiographically-obtained IVST, PWT, LVDd and LV mass in 45 cases of hypertention (HT), 25 of aortic regurgitation (AR), 20 of hypertrophic cardiomyopathy (HCM) and 45 normal subjects. In most cases, Rmax (the highest point of maximum) was located at V(4) and V(5), though occasionally above, below or left of V(4) and V(5). Smax (the highest point of minimum) was located below V(2) and V(3). The Rmax voltage and Smax voltage were significantly greater in the three disease groups. The Rmax voltage correlated roughly to the LVmass (r=0.55), as did the Smax voltage (r=0.67). Though there was no correlation between IVST and the time reflecting septal activation (time for Rmax to move to the left midclavicular line) in maps, the time in HCM was much longer compared to that in HT. Furthermore, the maximum voltage of the R wave in the left back leads (left scapular line) correlated to PWT (r=0.69, p<0.01). These results indicate the usefulness of bedy surface isopotential maps for presuming underlying disorders of LVH and for estimating the left ventricular posterior wall thickness.