Proteolytic enzyme in serum and urine was measured and it's clinical significance was observed on diseases of the liver and bile ducts. And the results were as follows. 1. In diseases of the liver and bile ducts, the value of serum proteolytic enzyme showed relatively high and urinary proteolytic enzyme also showed the positive rate of 40%. 2. As for the value of serum proteolytic enzyme, the activity value was high in mechanical jaundice, hemolytic jaundice, acute hepatitis and liver cirrhosis and it was moderate in liver cancer, cholecystopathy and chronic hepatitis. 3. Urinary proteolytic enzyme showed the activity in mechanical jaundice, hemolytic jaundice and helatosplenic syndrome and it was found over 40% in the cases showing the activity of urinary proteolytic enzyme, i.e. mechanical jaundice, hemolytic jaundice, posthepatic syndrome and acute hopatitis etc. 4. In mechanical jaundice, the value of serum proteolytic enzyme was 61.6 unit on the average and it showed the highest value in liver diseases, and the value of urinary proteolytic enzyme showed the activity value in 75% of the cases and it was the highest rate and it was interested in making the differential diagnosis of jaundice. 5. The value of serum proteolytic enzyme showed the distinct relation with the serum bilirubin and serum alkaliphosphatase, but it did not show any relation with the total serum protein and serum colloidal reaction.