A long-term study on the chemical and physiological changes of serum and thoracic-duct lymph in the dog with a ligated common bile duct and/or artificial liver circulation was performed. The influencee of ligation of the common bile duct appeared earlier in the thoracic-duct lymph than in the serum. The portal pressure did not increase in the dog with a ligated common bile duct, but the lymph flow of the thoracic duct was 3 times that before ligation, which would prevent the rapid stagnation of bile pigment in the liver. The portal pressure was not elevated after ligation of the hepatic artery. The cholesterol level in the thoracic-duct lymph was about half of that in the serum. In the dog with ligature of the common bile duct, the serum total cholesterol level was elevated with the elevation of serum bilirubin, whereas that in the lymph of the thoracic duct was not elevated with the elevation of the bilirubin level in the lymph. These findings suggested that cholesterol would not easily enter into the lymphatic route. The serum GPT level increased during the first week after ligation of the hepatic artery, and decreased thereafter. However, after ligation of the common bile duct, the GPT level increased for several weeks after the first week of ligation. The pattern of GPT by both ligations seemed to be cross-crossed. The marked change in the total bilirubin level in the lymph of the thoracic duct suggested its close relation with the lymphatic system. It was proved possible to secure a tube into the thoracic duct for over three weeks by the use of a U-type connector and jacket-type plaster cast.