The effects of vegetable oils (soybean oil and coconut oil) and C₁₈-unsaturated fatty acids (oleic acid, C_18:1; linoleic acid, C_18:2; linolenic acid, C_18:3) on plasma ethanol levels in male rats (6 weeks old) were investigated. Vegetable oils decreased and delayed the peak of plasma ethanol concentration: a dose-response to vegetable oils was observed in the concentration and time to maximum concentration of plasma ethanol but no change in disappearance time. These phenomena were observed in two conditions: 1) oral administration of vegetable oils before oral intubation of ethanol and 2) simultaneous oral administration of vegetable oils and ethanol. Similar responses were obtained in three C₁₈-unsaturated fatty acids. No changes in hepatic alcohol and aldehyde dehydrogenase isozyme (high Km and low Km) activities were observed. The remaining rate of ethanol in stomach was significantly higher with administration of vegetable oils or linoleic acid. A high negative correla-tion between the maximum plasma ethanol concentration and the remain-ing rate of ethanol in stomach was found. These results suggest that the slowing of the gastric emptying is a major mechanism for the decreasing and delaying effects on plasma ethanol levels by vegetable oils. The present paper also suggests that fatty acids may participate in the decreas-ing and delaying actions on the peak of plasma ethanol concentration by vegetable oils.