This study was intended to observe the changes in serum ceruloplasmin concentration after the ligation of common bile duct in rats. Several values of liver function tests are compared with the changes observed. Then the effects of actinomycin D administered rats, treated in the same method, were also observed for comparison. Common bile duct ligation in the rats brought about a rapid increase in serum ceruloplasmin concentration. Serum ceruloplasmin show ed an increase: of 2, 2.5 and 3 fold at the 2nd, 3rd and 6th day respectively following the bile duct ligation. But the increase was observed markedly inhibited in the case of administration of actinomycin D ($50{mu}g/100g$ of body weight) one hour prior to and eighteen hours after the ligation of the common bile duct in rats. After the ligation of common bile duct, the levels of serum alkaline phosphatase increased rapidly. This continued to be high throughout the experiments. The increase of serum alkaline phosphatase was significantly diminished with additional actinomycin D treatment. Serum glutamic pyruvic transaminase increased strikingly after ligation of common bile duct but the increase was not so obvious when adminstered with actinomycin D. The levels of serum total bilirubin increased sharply after the tigation of the common bile duct. The above results suggest that the bile duct ligation may cause the induction of serum ceruloplsmin and this is assumed due to the increase of the apoceruloplasmin biosynthesis.