Hemodynamic effects caused by ethanol infusion systemically in dose of 75 mg per kilogram per minute for 20 minutes have been studied in anesthetized open-cest dogs, and following results were obtained. Cardiac output, stroke volume and heart rate did not change and total peripheral resistance decreased with a fall in systemic blood pressure. Reduction in coronary vascular resistance, as same as a fall in total peripheral resistance, was observed with no change in coronary blood flow. Diminished left ventricular function, manifested as rise in end-diastolic pressure and a decline in deflection of segmental contraction curve of left ventricle, was observed in most cases. Isoproterenol (0.1μg/kg) injected intravenously after the in fusion of ethanol, produced a rise in systolic blood pressure and an elevation in left ventricular end-diastolic pressure (LVEDP), while a fall in blood pressure and a decline in LVEDP were caused with the intravenous injection of isoproterenol before the infusion of ethanol. Effects of isoproterenol on heart rate and cardiac output after the infusion of ethanol gave no essential change when compaired with those obtained without ethanol infusion. It is concluded that ethanol dilates both of coronary and systemic arteries with depression of left ventricular function, and makes a remarkable rise in left ventricular work when a positive inotropic stimulant such as isoproterenol was given, though an increased cardiac output caused by the stimulant was not influenced with ethanol essentially.