Acute hemodynamic changes induced by Betaxolol (B.) were studied in 10 patients (7 men, 3 women, mean age: 36 years), with uncomplicated essential hypertension. The brachial artery was cannulated with a short Teflon catheter and Swan-Ganz catheter was introduced into the pulmonary artery. Brachial (BAP) and Pulmonary arterial pressures (PAP), cardiac output (dye dilution) were recorded before (To) and after intravenous infusion of B. (0.2 mg/kg) during 5 minutes (T1), followed by the infusion of B. at a rate of 0.4 mg/kg during 15 minutes (T2). Cardiac index (C.I.), Stroke index (S.I.), Systemic Vascular (SVR) and Pulmonary Vascular Resistances (PVR), Left Ventricular Stroke Work Index (LVSWI) were calculated. C.I. declined significantly. This resulted from a significant decrease of heart rate, since S.I. was unsignificantly changed. BAP (systolic and mean) decreased significantly, since unsignificant changes of PAP were noted. SVR and PVR were significantly increased and LVSWI was significantly decreased. Plasmatic Renin Activity was unsignificantly decreased.