Eicosapentaenoic and docosahexaenoic acids were distributed mainly in the sn-1 and 3 positions of seal oil triacylglycerols and in the sn-2 position of fish oil triacylglyc-erols. Seal oil-rich or fish oil-rich fats having constant polyunsaturated (PUFAs)/monoun-saturated/saturated fatty acids and n-6/n-3 PUFAs ratios were fed to hamsters for 3 weeks. The control fat contained linoleic acid as the sole PUFA. The concentration of triacylglyc-erols in the liver was significantly lower in the fish oil group than in the control group. Phospholipid concentration in serum was lower and that in the liver was higher in the seal oil group compared with the fish oil group. The activities of fatty acid synthase (FAS), glu-cose-6-phosphate dehydrogenase (G6PDH), and the malic enzyme were significantly lower in both the fish and seal oil groups than in the control group. Dietary seal oil more effec-tively reduced arachidonic acid content in liver phosphatidylcholine and phos-phatidylethanolamine and serum phosphatidylcholine than fish oil. These results showed that different intramolecular distribution of n-3 PUFAs influenced glycerolipid metabolism and arachidonic acid content in serum and liver phospholipids of hamsters.