We assessed the effects of ethanol and autonomic blockade on left ventricular function in nine normal subjects, age 20--35 years, using M-mode echocardiography and systolic time intervals. On day 1, measurements were made of heart rate, mean velocity of circumferential fiber shortening, and left ventricular pre-ejection period and left ventricular ejection time ratio (PEP/LVET), during a control period and after autonomic blockade. Autonomic blockade was produced with intravenous propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg body weight). On day two, measurements were again made during a control period, then with ethanol alone, followed by addition of autonomic blockade to ethanol. One hundred eighty milliliters of ethanol were ingested over 60 minutes, resulting in a mean blood ethanol level of 110 mg/dl (range 77--135 mg/dl) at 60 minutes post-ingestion. There were no significant differences between the control data on days 1 and 2. Blood pressure was unchanged throughout the study. study. On day 1, autonomic blockade alone resulted in the expected increase in heart rate (p less than 0.001), with a proportional increase in mean velocity of circumferential fibr shortening (p less than 0.01), and an increase in PEP/LVET (p less than 0.01). On day 2, ethanol alone resulted in no significant changes except for a slight increase in PEP/LVET (p less than 0.02). Ethanol plus autonomic blockade, (day 2), compared with autonomic blockade alone (day 1), revealed a decrease in mean velocity of circumferential fiber shortening (p less than 0.05), and an increase in PEP/LVET (p less than 0.01), with a decrease in intrinsic heart rate (p less than 0.001). We conclude that in normal subjects: 1) autonomic blockade does not directly affect contractility; 2) acute ethanol ingestion alone does not produce important changes in cardiac function; and, 3) ethanol in the autonomic blockaded heart causes a significant decrease in contractility. Thus, we infer that ethanol has a negative inotropic effect which is masked by catecholamines and/or autonomic nervous system discharge.