In a 12-week, randomized, double-blind study, 24 patients with essential hypertension were given the angiotensin II antagonist losartan, or the beta-adrenoceptor blocker atenolol. Both drugs reduced blood pressure (BP) well, but losartan tended to reduce left ventricular mass (LVM) in contrast to atenolol. Following the double-blind phase 19 patients entered an open treatment period with losartan and additional treatment if BP was uncontrolled. LV structures were measured by echocardiography. The mean follow-up period was 29 +/- 2.6 (range 26-32) months. BP was reduced from 155.6 +/- 15.6/103.4 +/- 5.2 mm Hg to 131.3 +/- 10.5/82.7 +/- 3.3 mm Hg (P