In 19 patients with arterial hypertension the hemodynamics were determined with a Swan-Ganz-thermodilution catheter at rest and during supine ergometer exercise before and after 5 mg intravenous Propranolol (P) (10 pats.) respectively 10 mg of intravenous Metoprolol (9 pats.). During exercise, P caused a significantly higher increase in pulmonary capillary wedge pressure (PCP) (15.0 +/- 4.0 to 25.3 +/- 4.0 mm Hg), than M (10.9 +/- 4.8 to 17.4 +/- 5.5 mmHg) (p less than 0.025). There was a uniform reduction of the cardiac output (CO), after P and M. P caused a reduction of the CO by a decrease in heart rate and stroke volume, M through a significantly greater decrease in heart rate (p less than 0.0005), without a change in stroke volume (p less than 0.05). The changes in PCP and stroke volume give evidence of a more negative inotropic effect of P compared to M.