Blood coagulation and lysis system was studied with other biochemical serum analysis in three groups of mongrel dogs; laparotomy without hepatic resection (group I), with 50% hepatic section (group II), and 70% hepatic resection (group III). In clinical studies, six cases of hepatic tumors and one case of hepatoma with cirrhosis were selected for examinations. All the data examined in group I were restored toward normal within 48 hours. Total serum protein level was significantly decreased after hepatic resection. The protein level in group III was lower than in group II on the 4th postoperative day (P less than 0.01). In clinical studies, low serum protein levels did not reach a preoperative value even 3 weeks after extended right hepatic lobectomy. Time course of Al-P and transaminase changes in clinical studies was similar to that in experimental study with dogs. Al-P and transaminase showed an abnormally high level in the patient with hepatic cirrhosis. Serum bilirubin levels were not increased after hepatic resection. In blood coagulation and lysis system, serum fibrinogen levels were markedly decreased: 50% reduction in group III and 30% reduction in group II on the first postoperative day. The degree of decrease in the fibrinogen level was proportional to the size of resected volume of the liver. On the other hand, in clinical studies fibrinogen levels were slightly decreased. In the case of hepatic resection with cirrhosis, however, the values were markedly decreased: 40% reduction on the 4th and 25% on the 21st postoperative days. Fibrinolysis system was accelerated group II and III. The acceleration continued until 3 weeks after hepatic resection. From these results it may be concluded that analysis of blood coagulation and lysis system after hepatic resection is useful in evaluating a residual hepatic function after partial resection and in selecting a treatment suitable for hepatic insufficiency.