While the literature on smallpox is enormous, the subject has not been taken up before the American Dermatological Association for many years,1and this account of the Minneapolis epidemic is given because of its extreme virulence and to show once more the value of vaccination. EPIDEMIOLOGY2 The Minnesota law requiring vaccination was repealed in 1903, and since that time a large part of the population has come to be unprotected against smallpox. Health authorities believed that the mild type of smallpox might become malignant, until experience through many years proved that distinct strains exist, one a benign, or mild, type which never becomes truly malignant; the other a malignant type which never becomes truly mild. The fact that cases with mild symptoms may be of the malignant type has been shown repeatedly in the past epidemic when persons exposed to a fatal case of hemorrhagic smallpox developed only