The effects of age and dietary fatty acid composition on lipid metabolism were investigated in Sprague-Dawley strain male rats. These animals weighing 88.6$pm$2.2g were fed 10% dietary fat(W/W, 20% of total energy) with 0.5, 1, 2 P/S ratio and in each P/S ratio there were three different levels of n-6/n-3 fatty acid ratio ; 2, 4, 8. The experimental period was 1 month, 6 months and 12 months. The results of this study were as follows. The body weight of rats increased rapidly for the first two months, then increased slowly until 7 to 8 months. After 10 months of dietary regimen their weight decreased. The weight of liver, kidney and epidydimal fat pad increased along with the body weight and then decreased in the 12 months. Plasma total lipid increased with age and it decreased significantly when P/S ratio of dietary fatty acid was high. In creased with age and it decreased significantly when P/S ratio of dietary fatty acid was high. In creasing n-3 fatty acid intake in each P/S ratio resulted in lower plasma total lipid although was not statistically significant. The amount of plasma total cholesterol increased at 6 months, but decreased at 12 months. In case of 1, 12 months, increasing P/S ratio significantly plasma total cholesterol and LDL-cholesterol were decreased and hepatic cholesterol was increased, VLDL-HDL-cholesterol did not changed. The n-6/n-3 ratio did not affect any of theses. The amount of plasma triglyceride and VLDL-triglyceride increased at 6 month then decreased. When the rats consumed higher amount of n-3 fatty acid in each P/S ratio, their plasma triglyceride and hepatic triglyceride increased at 1, 12months.