Since the beginning of World War II there have been many advances in the fields of active and passive immunization which justify a review of current trends in methods of protection in everyday use by the practitioner. While this paper is concerned primarily with immunization in the pediatric age group, immunization of adults will be discussed when recommendations differ from those advised for infants and children. DIPHTHERIA, TETANUS, PERTUSSIS, AND SMALLPOX With low carrier rates prevailing in all but a few areas of this country, the stimulus necessary to keep our population immune to diphtheria must be provided artificially. Thirty to fifty per cent of our adult population is susceptible1 to diphtheria, and newborn infants of susceptible2 mothers likewise are susceptible. Infants should be protected as soon as feasible. Pertussis still is a severe and prevalent disease to which most newborn infants are susceptible, and they should receive