This study examines the effects of AAF levels and BHT on lipid peroxide metabolizing enzymes in rats fed different dietary fats. Weanling Sprague Dawley male rats were fed beef tallow and soybean oil at 15% with or without 0.3% BHT for 8 weeks. At 9th week, AAF was injected at the level of 25 ㎎ and 100 ㎎/㎏ body weight. The lipid peroxide values and cytochrome P-450 contents were determined in liver microsomal fraction, and SOD, GSH peroxidase, GSH S-transferase activities in cytosolic fraction. Effects of AAF on lipid peroxide values and SOD activities were not significantly different. GSH peroxidse activities and cytochrome P-450 contents were elevated at 25 ㎎ AAF in both dietary groups. At 100 ㎎ AAF, GSH peroxidase activities were lowered in soybean oil group, but elevated in beef tallow group. GSH S-transferase activities were elevated by AAF and correlated to the levels of AAF positively in both dietary groups. These results suggest that polyunsaturated fat diet and AAF might increase microsomal lipid peroxidation, but GSH peroxidase and GSH S-transferase activities were elevated by lipid peroxide and metabolized lipid peroxide effectively.