Six healthy men, aged 23 to 30 years, were studied by radionuclide angiocardiography at rest and at 2 submaximal exercise levels in the upright position during increasing alcohol intoxication. At light intoxication (serum ethanol 23 mmol/liter), the median value of left ventricular (LV) ejection fraction (EF) at rest decreased by 5%. At heavy intoxication (serum ethanol 45 mmol/liter), the median LVEF decreased at rest by 11% and during 75% submaximal exercise by 6%, heart rate at rest increased (median 81 vs 62 beats/min), and systolic blood pressure decreased during 50% submaximal exercise (median 145 vs 163 mm Hg). No significant changes of plasma epinephrine concentrations were recorded, whereas plasma norepinephrine concentrations were increased by 24% at rest during light intoxication and by 30 to 38% during heavy intoxication. No changes of LVEF and plasma catecholamine levels were recorded after ingestion of isovolumic, isocaloric drinks as compared with values obtained before intake. Thus, influences of ingestion per se and repeated investigations of LV function were excluded. These findings suggest that in healthy subjects alcohol intoxication causes a dose-dependent impairment of cardiac contractility. Compensatory mechanisms may account for a reduced influence during exercise.