Thirty male patients with ischemic heart disease and cardiomyopathy entered a controlled study of the acute effects of alcohol on cardiac function evaluated by right heart catheterization. Twenty patients, nine with angina pectoris and 11 with congestive heart failure, were studied during alcohol intoxication, and ten patients, five with angina pectoris and five with heart failure, served as a control group. The mean serum ethanol concentration in the alcohol group was 93 mg/100 ml (S.D. 17). The systemic arterial blood pressure was reduced by 6% in the alcohol group, P less than 0.05 compared with the control group. No significant changes occurred in the central venous pressure, the pulmonary artery pressure, the pulmonary capillary wedge pressure, or in cardiac output, stroke volume and total peripheral resistance. Alcohol intake in moderate doses has no measurable effect on pulmonary blood pressures or cardiac output in patients with ischemic heart disease and cardiomyopathy. Such an effect may, however, be masked by a reduction of afterload.