A clinical study of the efficiency of a new beta-blocker, chloranolol (Tobanum, Hungary), was carried out in 24 patients with second-stage essential hypertension. Central and intracardiac hemodynamics, left-ventricular myocardial function (echocardiography) and regional hemodynamics (occlusion plethysmography) were assessed in 14 patients before treatment and on days 10-15 and 25-30 of chloranolol administration. During the fourth or fifth week of chloranolol treatment, arterial BP diminished by 12/10% (p less than 0.01) owing to an 11.5% reduction in the cardiac index and a 15.7% reduction in heart rate (p less than 0.001), while the stroke index and total peripheral resistance showed no significant change. No basic changes in end diastolic and systolic left-ventricular size and volume, nor in the ejection fraction were seen during treatment. Myocardial contractility dropped by 9.8% (p less than 0.05), and intramyocardial tension, by 14% (p less than 0.001), while the thickness of the interventricular septum declined by 7% (p less than 0.001), and that of left-ventricular posterior wall, by 4.2% (p less than 0.005). Chloranolol treatment was particularly efficient in moderately hypertensive patients and also in some highly-hypertensive ones that had not responded to propranolol.