One hundred and ninety-five patients with diastoiic systemic hypertension over 90 mm Hg were studied by serial echocardiography over five years of treatment. Satisfactory studies were obtained in 68 subjects with uncomplicated, untreated hypertension. In this group of patients during the five year period, there were significant decreases in systolic and diastoiic pressure that were associated with significant decreases in heart rate, left ventricular septal and posterior wall thickness, left ventricular end-systolic volume, left ventricular mass and the ratio of mean left ventricular wall thickness to left ventricular ratio. There were significant increases in the left ventricular end-diastolic volume, left ventricular stroke volume, fractional shortening of left ventricular enddiastolic diameter and ejection fraction. Echocardiography was more specific and sensitive in detecting the presence and the regression of left ventricular hypertrophy than either electrocardiography or the chest X-ray. The chronic treatment of systemic hypertension is associated with echocardiographic evidence of regression of left ventricular hypertrophy and of improvement in ventricular function.