81 subjects including 35 cases of acute hepatitis, 20cases of chronic hepatitis, 16 cases of liver cirrhosis, and 10 normal controls were selected for studying the glucuronic acid conjugation and bilirubin glucuronide formation in the subjects with liver diseases. Benzoic acid was administrated in every cases and the fractions of whole benzoic acid, hippuric acid and benzoyl glucuronide in the urine excreted within 6 hours were determined and the results obtained were compared with serum bilirubin glucuronide fraction or the results of liver function tests. The results were as follow. 1. In case that 4g of benzoic acid was administered, no more than 5.3% were conjugated to benzoyl glucuronide, however, when 5g was gigen, the conjugation rate increased to 10.7% in the average value. Then 4g administration was used for this experiment. 2. Although the excretion of total benzoic acid and hippuric acid showed the relative increase, the benzoyl glucuronide formation was found to be diminished in the cases of non icyeric acute or chronic hepatitis and liver cirrhosis. 3. In the icteric stage, the excretion of whole benzoic acid or hippuric acid showed decrease as compared to the non icteric stage, while, benzoul glucuronide formation was found to be increased in the cases of acute or chronic hepatitis, however, no change or a little decrease was observed in the case of liver cirrhosis. 4. The excretions of whole benzoic acid, hippuric acid and benzoyl glucuronide were all decreased in the severe stage of hepatitis, however, the excretion of benzoic acid showed more marked increase as compared to that of hippuric acid excretion as the patients recovered, besides, benzoyl glucuronide excretion also increased with recovery. When the recovery of the patients more progressed the excretion of benzoic acid or hippuric acid became almost normal, on the contrary the benzoyl glucuronide formation decreased. 5. Although the relatively good correlation was observed between benzoyl glucuronide formation and the serum colloidar reactions (TTT, ZnTT, CoCl(2)), no significant correlation could be found between the serum colloidar reactions and the percentage of benzoyl glucuronide to whole benzoic acid excreted. No significant correlation could be found between benzoyl glucuronide and serum alkaline phosphatase or S-GOT, S-GPT. 6. Any significant correlation could not be observed between benzoyl glucuronide formation and the molar ratio of glucuronic acid contained in ester form bilirubin.