To evaluate the relationship between the distribution of hypertrophy and the electrocardiographic findings in patients with hypertrophic cardiomyopathy (HCM), 54 HCM patients were studied using magnetic resonance imaging. The patients were divided into 4 groups according to hypertrophic patterns: (i) hypertrophy only at the apex (group I, n=12); (ii) hypertrophy in both the apex and base (group II, n=20); (iii) hypertrophy only at the base with asymmetric septal hypertrophy (ASH) (group IIIa, n=17); and (iv) hypertrophy only at the base without ASH (group IIIb, n=5). Abnormal Q waves in leads II, III and aV_F were found in 1/12, 3/20, 10/17 and 0/5, respectively, and in leads I and aV_L they were found in 1/12, 8/20, 4/17 and 1/5, respectively. The largest negative T waves (mm) were found in group I (group I vs group II vs group IIIa vs group IIIb: 15.2±5.3, 8.2±6.1, 1.6±2.0, 0.8±1.3, respectively). The largest positive T waves (mm) were identified in group IIIb (3.8±3.0, 6.8±3.2, 5.8±3.6, 9.3±2.1, respectively). The presence of abnormal Q waves reflected regional hypertrophy in HCM patients but the configuration of T waves represented the difference in the localization of hypertrophy between the basal and apical segments. (Jpn Circ J 1998; 62: 483 - 488)