In 1945 Krehl et al. made the important discovery of the relationship of niacin and tryptophan and their experiments were extended to investigation of amino acids imbalance. Pecora and Hundley have reported that the rate of body weight gain of rats fed a rice diet supplemented with lysine and threonine was greater than that of the control group receiving rice alone. The authors abstracted rice protein from the rice, and prepared the rice protein diets of varying amount of rice protein supplemented with lysine and theonine, or glycine and methionine. These diets were fed to the rats, and following results were observed. 1. The body weight of rats fed a 7.5% rice protein diet supplemented with lysine and threonine was less decreased than in the control group receiving 7.5% rice protein diet alone, and the rate of body weight gain of rats fed a 10% or 15% rice protein diet supplemented with lysine and threonine was greater than that of the control group receiving 10% or 15% rice protein diet alone. 2. No difference was observed between the rate of body weight gain of rats fed 75. % rice protein diet supplemented with glycine and methionine and that of rats receiving 7.5% rice protein diet alone. But the rate of gain of rats fed 15% rice protein diet supplemented with glycine and methionine was greater than that of the control receiving 15% protein diet alone. 3. No difference was observed between the vitamin C level in blood and liver of rats fed the diet supplemented with lysine and threonine and that of rats fed the protein diet alone. 4. The vitamin C in blood of rats fed the diet supplemented with glycine and methionine seems to be a little higher than that of the control group fed the protein diet alone. But no difference was observed between the vitamin C level in liver of the experimental rats fed the diet supplemented with glycine and methionine and that of control group fed the protein diet alone.