As the cause of hereditary or familial diabetes is of interest for the subjects of both diabetes and heredity, the opportunity was taken of making some observations concerning it is one case on the diabetic service of this hospital.REPORT OF CASEFamily History.—The family are "poor whites" in a little mountain hamlet of South Carolina, and offer three features of special interest for a study of heredity. First, is the isolation of the community, the absence of immigration, and the thorough knowledge concerning their ancestry and relatives for several generations back. Second, is the large size of the family, and the remarkably high incidence of diabetes encountered in one generation. Third, is the fact that before his marriage to the mother of the present family of children, the father had had an illegitimate child by another woman, which developed diabetes, though that woman and her family were free