We studied the effect of the fatty acid composition of commercially available cooking oil added to a high-cholesterol diet on the serum and liver lipid concentrations and hepatic acid composition in rats fed with the diets. Rats were fed one of three diets respectively containing the following three types of oil : diet 1, oil rich in saturated fatty acid; diet 2, oil rich in a-linoleic acid; and diet 3, oil rich in diacylglycerol. The weight gain among the three diet any groups did not significantly differ. The total food intake was most for the diet 1 group, while serum cholesterol was highest and the ratio of HDL-cholesterol/total-cholesterol was lowest in this dietary group. Serum triglyceride was lowest in the rats fed with diet 3, and the hepatic fatty acid composition in the liver reflected that of the diet. The dietary fatty acid composition in food and the lipid metabolism need to be carefully considered when providing a high-cholesterol diet.