A group of young male rats, maintained with the artificial diet containing 40 per cent of SrCO₃and administered daily 30 mg per kg of cortisone acetate simultaneously for three weeks, were compared with normal diet, 40 per cent of SrCO₃diet, and 30 mg per kg of cortisone acetate administered groups respectively. The increase of body weight in the group of rats given SrCO₃plus cortisone was markedly suppressed compared with those of rats given SrCO₃or cortisone respectively. The ratio of ash content in femurs was minimum in the group of strontium rachitic rats and indicated the retardation of calcification, while the ratio was little greater in cortisone treated group compared with control one. In the strontium plus cortisone group, however, the ratio is greater than strontium treated one. From this fact it may be said that cortisone acts antirachitogenic. In roentgenogram, the endplates of tibiae were separated transversely in strontium rachitic rats and the width of meta-epiphyseal line was reduced in rats given cortisone, while epiphyseal figure of rats given strontium plus cortisone mediated above two forms. The roentgenogram of the lower extremities of rats treated cortisone plus strontium may corresponded to the histological findings, which show the increase of cartilaginous plate due to the decalcification observed in the storontium rachitic rats and a marked extension of newly reformed trabeculae attributed to the retardation of resorption of bone following the cortisone treatment. Citrate content of bone did not show any appreciable change in rats treated cortisone plus strontium, while a marked reduction was observed in strontium rachitic rats. Glucosamine content of femurs decreased in order strontium rachitic animals>strontium plus cortisone>control>cortisone. This indicates that in strontium plus cortisone treated group the increased tendency of glucosamine content in rachitic animals is canceled with the decreased tendency of that in cortisone treated animals.