Young male rats were fed for 10 and 20 days on different low-fat experimental diets ; 4% lard + 4% soybean oil, 4% sardine oil + 4% lard, 4% sardine oil with vitamin E+ 4% lard, 4% sardine oil with vitamin E+ 4% soybean oil. Lipid peroxide levels in liver were significantly higher in the sardine oil groups but the addition of vitamin Ehad no effects on the lipid peroxide values. Serum total cholesterol showed no significant difference among the groups but HDL-cholesterol in serum was increased in the sardine oil groups. However, the contents of serum triglyceride and phospholipid were unaffected by the replacement with sardine oil.