Surface electrocardiographic findings of 10 cases of left bundle branch block with echocardiographically determined left ventricular hypertrophy were compared with another 10 cases of left bundle branch block without left ventricular hypertrophy. Horizontal plane QRS- and T-wave angle greater-than-or-equal-to 150-degrees was highly sensitive (70%) and specific (90%) in diagnosing left ventricular hypertrophy in the presence of left bundle branch block. This diagnosis criterion was better than any other conventional criterion described before.