In 307 patients with diabetes mellitus, developed prior to 1933 and before age 31 it was demonstrated that: (1) frequent contact with a specialized diabetes clinic from an early stage of the disease; (2) a good quality of "metabolic control"; (3) a low insulin dose; (4) a body weight of 10% less than ideal; and (5) a mean blood pressure below 100 mm Hg, all had significantly beneficial effects upon the survival. It was also found that patients domiciled in Copenhagen had a significantly better prognosis than patients domiciled outside Copenhagen. Frequent contact with a diabetes centre was accompanied by an appreciable decrease in disabling late diabetic complications.