Experiments were undertaken to determine the value of Yatoconin, a calcium salt of fructose-6-monophosphoric acid ester, in rickets of young growing rabbits was given subcutaneously. All the control animals which were fed the ricketsproducing diet, without exception developed rickets. In the small series of animals received Yatoconin developed rickets in somewhat slighter degree and showed a slightly better increase of both body weight and bone length than that of the control animals, although in the large series of the animals developed rickets to the same extent as the control animals.