The combined effects of ethanol and components in fresh garlic on ethanol metabolism were investigated in the livers of mice. Male, I 1-wk-old C3H/HeNCrj mice were intragastrically administered 2g ethanol/kg body weight after being administered fresh garlic juice for 8 d (garlic group), and changes in the concentrations of ethanol, acetaldehyde and acetate in the serum, and changes in the activity of hepatic enzymes related to ethanol metabolism in mice were examined. The increases in the concentrations of acetaldehyde and acetate in the serum after ethanol administration tended to be diminished following garlic administration. The microsomel ethanol-oxidizing system (MEOS) in the livers of the garlic groups was significantly lower than that of the control microsomes at 2h after ethanol administration. It therefore seems that the decrease of MEOS in hepatic microsomes caused a smaller increase in the acet-aldehyde concentration in the serum of the garlic groups because cyto-solic alcohol dehydrogenase showed no significant difference between the control and garlic groups. After ethanol administration, the content of cytochrome P-450 in the hepatic microsomes of the control groups increased, while that of the garlic groups did not change although cytochrome P-450 (CYP) 2E1 and 1A2 in the hepatic microsomes of the garlic groups increased. These results indicate that the induction of isozymes of cytochrome P-450 other than CYP 2E1 and 1A2 was inhibited following garlic administration. Cytosolic high Km and total aldehyde dehydrogenase (AJDH) in the liver of the garlic groups tended to be lower than those activities of the control groups at 1 and 2h after ethanol administration. It therefore seems that the decreases of AIDH in the hepatic cytosols diminished the increase of acetate in the serum of the garlic groups after ethanol administration. These results suggest that the ethanol metabolism in the mouse liver is controlled by components in fresh garlic juice.