Naloxone hydrochloride (2.0 mg/kg) has been found to reverse the significant decreases in the hepatic cytosolic and mitochondrial [NAD+]/[NADH] ratios observed after acute ethanol administration in rats. This correction of the ethanol-induced changes in the hepatocellular redox state by naloxone was, however, not associated with any lowering of serum ethanol concentrations or an observable reduction in the extent of intoxication. This lack of antagonism of alcohol intoxication by naloxone was not affected by the feeding status of the animals, the time point after naloxone administration at which serum ethanol concentration was determined or the method used for ethanol analysis. Thus this study has failed to confirm that naloxone antagonises acute alcohol intoxication, in spite of its potent ability to reverse the ethanol-induced changes in the hepatic redox state.