This study was designed to observe the effects of the fish oil and some seed oils on the improvement of the fatty acid compositions of liver and brain tissue in rats. In order to induce the hypertriglyceridemia in the rats of the Sprague-Dawley, 12% coconut oil and 3% each of olive oil, lard, fish oil, perilla oil, corn oil, red pepper seed oil and evening primrose oil were administered to the rats for 4 weeks. In the fatty acid composition of liver lipid, n-3 PUFA contents were most in the fish oil and perilla oil groups of phospholipid fraction, and n-6 PUFA contents were most in the corn oil, red pepper seed oil and evening primrose oil groups of triglyceride fractions. Fatty acid composition of liver lipid fractions were influenced from the fatty acid composition of the test lipids. In the fatty acid composition of brain phospholipid, n-3 PUFA contents (8.8~17.2%) were most in the fish oil group, and n-6 PUFA (34.6~38.2%), though it contains high percentage, showed little difference between groups.