The liver lipid components, plasma lipid levels, and platelet aggregation were determined, in rats fed experimental diets for 4 weeks. Fiftythree percent of the dietary fat in the linoleic acid (LA) group was 18: 2n-6, which was partially replaced by 18: 3n-6, 18: 3n-3, and n-3 polyunsaturated fatty acid (PUFA) in the γ-linolenic acid (GLN), α-linalenie acid (ALN) and fish oil (Fish) groups, respectively. The liver cholesterol level in the Fish group was significantly higher than the levels in the other groups, whereas the liver phospholipid level in the GLN group was significantly higher than the levels in the other groups. These results suggest that the effect of 18: 3n-6 on hepatic cholesterol metabolism may differ from that of n-3 PUFA. However, neither the plasma cholesterol level nor platelet aggregation induced by collagen was affected by dietary fat.