In order to elucidate the mechanism operating during the hypocholesterolemic action after the administration of anabolic steroids, cholesterol and bile acids were determined in the serum, bile and liver. About 100 male dogs of 10kg body weight were used at the experimental animals. The animals were divided into 3 groups: The first group was normal healthy dogs, the second was the dogs blocked the reticuloendthelial system with china ink, and the third was the dogs given carbon tetrachloride. Pyridoxal phosphate was given simultaneously to the dogs in about a half of the test animals. The results obtained were as follows; a) A reduction of serum cholesterol was observed in the healthy dogs by the administra tion of the anabolic steroido, the increased uptake of cholesterol into the liver as well as increased synthesis of trihydroxy cholanic acid and dihydroxy cholanic acid from cholesterol followed with increased excretion into bile were thought to be responsible for the reduction of serum cholesterol. b) The anabolic steroid had no hypocholesterolemic action when liver cell wasdamaged or reticulo-endothel system was blocked. c) The shift of cholesterol from blood the liver is related to liver cell and reticuloendothel system. d) Pyridoxal phosphate used with anabolic steroid resulted in no excretion of trihydroxy cholalic acid and dihydroxy oholalic acid in bile, be it seen when only the latter was administered. Pyridoxal phosphate is competitive to anabolic steroid. e) Pyridopal phosphate used with anabolic steroid had no such effect when the liver cell was damaged or reticulo-endothel system was blocked.