The distribution or the output in blood or urine of procaine used on surgical operation and its hydrolyzed products has been examined by the method described above. On using 0.875g of procaine hydrochloride as local and splanchnic anesthesia, the blood total amount of the compounds which is showing a diazo-reaction on basis of procaine was maximum during the first two hours, and decreased gradully after then. On the other hand, during these wo hours while the laparotomy was performed, the amount of procaine and its hydrolyzed products showing a diazo-reaction which was discharged into urine was only 0.5% of the total amount having been used here. P-amino benzoic acid, which is one of its hydrolyzed products, almost changed into its acethyl compound. The amount of non-hydrolyzed procaine discharged into urine was about 1% of the total amount which has been used, and almost all of them was discharged within the first six hours after used. The ratio of non-acethyl type of p-amino benzoic acid to acethyl type of p-amino benzoic acid was 1:9 in the first six hours. After the six hours almost all the p-amino benzoic acid was discharged in acetyl ype. The total amount of p-amino benzoic acid and its acethyl type outpoured into urine was 50% of the amount having been used or more in the first six hours, and about 80% in twenty-four hours.