Echocardiography was performed in 28 consecutive patients who manifested accepted criteria for left ventricular hypertrophy on their electrocardiograms. Four groups of patients were identified: Group 1, nineteen (68%) who had an increase in both interventricular septal and left ventricular posterior wall thickness; Group 2, three patients (11%) with isolated enlargement of the left ventricular internal dimension; Group 3, two subjects (7%) with increased septal thickness, left ventricular posterior wall thickness and left ventricular internal dimension and Group 4, four patients (14%) with normal echocardiographic measurements. It is concluded that increases in both septal and left ventricular wall thickness are the primary echocardiographic correlates of left ventricular hypertrophy as diagnosed on the electrocardiogram.