The influences of vitamin B(2) on uric acid formation were investigated with normal male guinea pigs by the administration of 50 mg of vitamin B(2) into semial vesicles through vas deferens. The experiments were performed exactly the same as stated in report 1 and the results were as followed. 1. The mean uric acid concentration in blood reached a peak at 15 minutes and gradually decreased at 5hours which was not still returned to normal. 2. The ability of uric acid formation was depended on the amount of vitamin B(2) to be administrated into seminal vesicles and these effects were much induced by large amount as illustrated in interval administration.