After administration of ethanol and pyrazole, a potent inhibitor of alcohol dehydrogenase, for 3 weeks to rats, enzyme activities of key glycolytic enzymes of the liver (glucokinase, hexokinase, glucose-6-phosphate dehydrogenase, pyruvate kinase), a key gluconeogenic enzyme, (glucose-6-phosphatase), and alcohol dehydrogenase were invesgated. The resulting enzyme patterns are as follows: In rats treated with ethanol alone, glucose-6-phosphate dehydrogenase activity was decreased and glucose-6-phosphatase activity was increased. In the group treated with pyrazole, activities of hexokinase and glucose-6-phosphatase were decreased. In the group treated with pyrazole and ethanol, the activity of glucose-6-phosphate dehydrogenase was significantly increased, and those of pyruvate kinase and glucose-6-phosphatase were significantly decreased. The enzyme patterns appear to be different from those in liver injured by alcohol or hepatotoxins. This result suggests that liver damage caused by ethanol and pyrazole is due not only to high blood alcohol levels, but also to a combined effect of pyrazole and alcohol in regard to hepatic microsomes.