Bile was collected with a duodenal tube from 14 controls and 45 cases with various liver diseases which were consisted of 8 cases with acute hepatitis, 10 cases with chronic hepatitis, 8 cases with cirrhosis of the liver, 4 cases with Gilbert's syndrome, 3 cases with Dubin-Johnson's syndrome and 12 cases with cholecystopathy. Bilirubin was extracted from the bile and separated with Billing's siliconized Kieselguhr column chromatography. Bilirubin-phosphate fraction showing positive phosphate ester reaction reported by Kondo, was fractionated with cellulose column chromatography as reported by Monobe, and finally its percentage to total direct bilirubin was calculated. Correlations between bilirubin-phosphate fraction and various liver function tests were studied and the following results were obtained. 1) Bilirubin-phosphate fraction was found to be 7.3% in cirrhosis of the liver, 5.5% in constitutional jaundice, 5.0% in acute hepatitis, 3.5% in chronic hepatitis, 2.2% in cholecystopathy and 2.1% in controls. Percentage of bilirubin-phosphate fraction was significantly higher in cirrhosis of the liver than in control, cholecystopathy and chronic hepatitis, and in acute hepatitis than in control and cholecystopathy. 2) There were good correlations among percentage of bilirubin-phosphate fraction, colloidal reaction (ZnTT, TTT) and serum γ- globulin fraction. 3) No significant correlations could be found among percentage of bilirubin-phosphate fraction, serum transaminase (GOT, GPT), cholesterol and alkaline phosphatase. 4) There was a good correlation between percentage of bilirubin-phosphate fraction and BSP retention at 45 minutes. 5) A significant negative correlation was obtained between percentage of bilirubin-phosphate fraction and K(ICG).