To investigate the electrocardiographic abnormalities of left ventricular hypertrophy (LVH), body surface potential maps were acquired from 42 patients with essential hypertension. We adopted the time integral technique for analyzing body surface mapping data and used echocardiographic left ventricular muscle mass (LV mass) as the index of advance of LVH. The QRS, ST-T and QRST isointegral maps in normal volunteers all demonstrated smooth bipolar surface distribution patterns, with positive values located over the precordium and negative values over the right upper chest and back. In patients with essential hypertension, changes in the isointegral maps were observed as LVH advanced; A QRS increased on the upper left lateral chest and decreased (became more negative) on the right chest, A ST-T decreased on the lower left lateral chest and increased on the right upper chest, and areas of significant difference in A QRS and A ST-T were expanded as LVH advanced. A QRST decreased on the lower left lateral chest and increased on the right upper chest only in patients with severe LVH. We conclude that the changes of QRS and ST-T isointegral maps depend on the degree of advance of LVH and the severe grade of LVH causes the alterations in intrinsic repolarization properties.