One of the striking features of the insulin treatment for diabetes mellitus is the uniformity with which even the most severe forms respond to the injections of insulin. From time to time, however, cases have been reported that seem relatively refractory to insulin. Some of them are more refractory than others, but none of them compare, in this respect, with a case we recently observed. Charlton 1 reported a patient with severe diabetes who, on a restricted diet, did not respond to 102 units of insulin. The patient was syphilitic, and after a course of antisyphilitic treatment responded readily to injections of insulin. Mahler and Pasterny 2 reported a case of diabetes mellitus in which a hypophysial tumor was present. Sixty units of insulin produced practically no effect on blood sugar or glycosuria but did produce a marked hydremia. Charles and Clarac 3 observed a case of diabetes mellitus in which a hypophysial