Infusion of ethanol (0.6 g/kg body wt) caused marked hypoglycaemia in subjects fasted for 36 h. Previous administration of the alcohol dehydrogenase (ADH) inhibitor 4-methylpyrazole (4-MP, 7 mg/kg body wt i.v.) strongly suppressed the ethanol-induced hypoglycaemia. The rate of ethanol elimination was 84.6 mg/kg per hour. 4-MP at the dose used caused a 21% reduction of ethanol elimination, but had no significant effect on blood acetaldehyde levels. 4-MP also significantly suppressed the ethanol-induced elevation of blood lactate and almost completely prevented the increase in the 3-hydroxybutyrate/acetoacetate ratio, but had only a slight effect on the lactate/pyruvate ratio of venous blood. The results demonstrate that the hypoglycaemia and lactacidaemia produced by the oxidation of alcohol can be prevented by a dose of 4-MP that diminishes or prevents the ethanol-induced shift in the NAD-coupled redox state of the liver.