Young mae rats were fed fro 4 weeks on different experimental diets containing 8%(w/w) fat ; sardine oil, soybean oil and lard. In the sarine oil group, total cholesterol and triglyceride concentrations inplasma were significantly lower than in the soybean oil and lard group. The proportion of $omega$-3 polyunsaturated fatty acids in erythrocyte membrane phospholipids were significantly higher in the sarine oil-fed animals. by sardine oil ingestion, lipid peroxide levels inthe plasma and liver were elevated while $alpha$tocopherol concentrations were lowered, compared to the other groups. However, erythrocyte osmotic fragility was unaffected by the different fat diets.