Effects of alprenolol, propranolol and practolol on hemodynamics were studied in open-chest anesthetized dogs, and following results were obtained; Coronary blood flow was decreased accompanied with a rise in coronary vascular resistance following the administiation of the drug. Cardiac output and heart rate were decreased, and total peripheral resistance was elevated significantly. Practolol produced lesser changes in coronary and systemic hemodynamics than alprenolol or propranolol; especially lesser elevation in total peripheral resistance and smaller decrease in maximun blood flow of aorta.