1. Young rats 'were fed on the ration containing 3 or 10 per cent of fattreated- urea (FU). The growth of rats was apparently suppressed proportionally to the amounts of FU administered, and this suppression was considered to be attributed to the decreased feed consumption of rats. About 98 per cent of the nitrogen in FU was digested and absorbed by rats. The liver and kidneys of rats fed on the ration containing 10 per cent of FU were a little enlarged and the content of protein in their liver was lowered in comparison with those of control animals. The contents of urea in the blood, liver and muscle of rats administered FU were higher than those of control animals, but the contents of hemoglobin in the blood and non-protein-nitrogen and fat in the liver and muscle were scarcely affected. 2. The growth of chicks fed on the ration containing 5 per cent of commercial urea (U) or FU was more suppressed than that of the control ones, but there was no difference between the diet containing U and FU. The weight and appearance of the liver and kidneys in chicks were not affected by the administration of U or FU. The contents of urea in the blood, liver and muscle of chicks administered U or FU were considerably higher than those of control animals, but there was no difference between the lots of U and FU. The urea in FU was found to be rapidly absorbed by the chicks as well as that in U, namely, the urea was remained unabsorb: d in the gizzard in amount of 12 per cent and in the under part of the small intestine in amount of only 2 per cent.