In 1968, 572 persons in the United States had confirmed vaccination complications. Of these, 82.5 per cent had received Vaccinia Immune Globulin. Sixty-eight per cent of the patients were primary vaccinees, 7 per cent were revaccinees, 20 per cent acquired vaccinia not by vaccination but by contact, and 5 per cent had unknown histories of vaccination. There were nine deaths: four caused by postvaccinial encephalitis, four associated with vaccinia necrosum, and one caused by eczema vaccinatum. There were 74 complications and one death per 1,000,000 primary vaccinations. Morbidity and mortality rates were highest for infants, with 112 complications and five deaths per 1,000,000 primary vaccinations. Eczema vaccinatum was more severe for contacts than for vaccinees. Although the risk with revaccination is less than a tenth that with primary vaccination, vaccinia necrosum develops in patients with immunologic disorders whether or not they have been previously vaccinated. These estimates, based on surveillance, must be considered minimal.