AbstractIn the past two years I have seen two babies, sisters, having from birth deformities like those of severe rickets. A few days after birth they began to have curious spells of sham joy. Both had a hypercalcæmia but normal or slightly reduced phosphatæmia without discernible progressive decalcification of the skeleton. One died at three months and the other at six. Both had early pathological changes in the kidneys, which would have led to chronic nephritis. At first I thought that these were cases of congenital osteitis fibrosa cystica, but now believe that the two children were suffering from a form of the disease variously called ‘renal rickets’, ‘dwarfism’, or ‘infantilism’. If this is true, then the cases add weight to the opinion that these diseases are due to endocrines running amok, the kidneys being but innoce