1) It was found that the polished rice is short of Iysine, methionine, cystine, and tryptophan among the essential amino acids, and that it shows no significant variations with regard to its pattern of geographical region. 2) Comparing in the contents of essential amino acids in the cereals, such as polished barley, wheat, great millet, and soy bean, the soy bean is found to be better than the polished rice, while the others to be either poorer or similar than the polished rice. 3) The aminal experiments observed with the mixed diet revealed that the most ideal composition of the mixed diet is the one composed of 70% polished rice, 20% polished barley, and 10% soy bean.