1. Pure biuret (97 %), crude biuret (isolated from heated urea and pure biuret was added to produce an 80 % biuret mixture), and heated urea (prepared by mixing heated urea and crude biuret to make a 50 % biuret mixture) were fed to various animals and theit effects were observed. 2. Milk goats were fed on rations containing 5 g of crude biuret for 5-20 days. There were no effects on their health nor on the fat and non-protein nitrogen of the milk. Goats were fed on diets containing 5 g of heated urea for 10 days, then, 10 g of urea were added to this ration for another 10 days. There were no effects on their health, but in some cases the amount of their water consumption increased. 3. Milk cows, f e d on normal rations containing 40 g of urea, were given daily either 20 g of crude biuret or 40 g of heated urea for 7-10 days. There were neither effects on their health, yield of milk or contents of fat and non-protein nitrogen in the milk, nor on the non-protein nitrogen content of the blood. 4. Sheep were given daily 5-10 g of heated urea for 5-10 days. Oth e r sheep were given 5 g of crude biuret and 30 g of urea for 10 days. In each of these cases there were no effects on their health nor on the content of non-protein nitrogen in the blood. 5. Daily, 10 g of heated urea were fed to horses for 10 days, 15 g of crude biuret to sows for 8 days, 3 g of pure biuret to adult rabbits for 7 days, and 10 g of heated urea to young rabbits for 30 days. There were no apparent effects on their health. 6. Adult albi n o rats were given 1 g of pure biuret every day with 14 g of rice and experiments on nitrogen metabolism were carried out. It was found that the biuret had been almost completely absorbed and then excreted in the urine, and that the nitrogen had not been retained in the rat body. In these cases, biuret content increased remarkably in the urine but very slightly in the blood.