Serum bile acids and bilirubins from patients with icteric liver diseases were fractionated and measured. The results were compared with non-specific liver function tests and liver biopsy specimens wherever possible. The degree of alteration in bile acids and bilirubin metabolism was related to the stage and/or type of liver disease. The method of serum bile acid measurement by Weber was also assessed. The results were as follows: 1) In Weber's method, methanol is in the liquid phase; however, this decreased the activity of 3a-hydroxysteroid dehydrogenase, so methanol was ommitted from the system. Sodium lauryl sulfate was ommitted also, because of its high fluorescence intensity. 2) The concentrations of total, non-sulfate & sulfate conjugated and glycodihydroxy bile acid were correlated with the concentrations of total, salt-form and ester-form bilirubin, and the molar ratio of glucuronic acid to ester-form bilirubin. Free bile acid did not correlate with indirect bilirubin. There was some difference in the correlation between bile acid fractions and bilirubin fractions. These results showed that the disturbance was of both bile acid metabolism and bilirubin metabolism in icteric liver disease, but that the degree was different. 3) The concentration of sulfate conjugated bile acid correlated well with alkaline phosphatase activity and cholesterol. 4) The ratio of free bile acid to total bile acid was lower in extrahepatic cholestasis than in intrahepatic cholestasis, but not to a significant degree. From bile acid fractions, there was no obvious difference between extrahepatic cholestasis and intrahepatic cholestasis. 5) In histological findings, many cases with elevated total bile acid showed liver cell necrosis and hyperplasia of Kupffer cells. There was no correlation between the histological findings and the concentration of total, sulfate conjugated, or free bile acid.