In a randomized double-blind study to compare the effect of atenolol vs. hydrochlorothiazide and amiloride (Moduretic) on left ventricular dimensions and systolic function, 100 hypertensive men were followed up during 1 year of treatment, 50 subjects being randomized to each drug. Echocardiography was performed at baseline, and after 3 and 12 months of treatment. A significant reduction in left ventricular mass with atenolol was paralleled by a decrease in left ventricular wall thickness and an increase in stroke volume. A similar reduction of left ventricular mass with Moduretic without a change in relative wall thickness and a decrease in stroke volume was observed. Cardiac output decreased in both groups.