Deaths from diabetes mellitus in Norway during 1898-1921 when distributed in various age groups, form two distinct intersecting curves, one representing early life and culminating at puberty, the other representing more advanced ages leading up to the sixty to seventy years' group, the total number of deaths recorded being 5,951. Mortality curves for men and women follow parallel lines in the younger and older age groups. Etiological factors influencing diabetes in the older age group are race, heredity, obesity, arteriosclerosis, nervousness and disturbances of internal organs; in the younger age group infections such as scarlatina, typhoid fever and epidemic parotitis, with subsequent parotitic pancreatitis, often lead to grave and rapidly fulminating diabetes. Parotitic epidemics in the young age group are followed by a rise in the death rate from grave diabetes in the young age group three to four years following each successive parotitic epidemic. Atrophy of testicles following parotitic orchitis is similar in nature to atrophy of pancreas following parotitic pancreatitis. "Acute diabetes" in youth, graver in type and more rapidly fatal than slower and milder development of diabetes in the older age group, is suggested by the author to be infectious in origin and probably caused by the virus producing epidemic parotitis.