Measles, a highly contagious viral disease, kills several hundred thousand infants and young children yearly. Essentially all children will become infected; at least 1% of those living in developing countries will die unless protected by immunization. In urban areas, peak incidence occurs in those younger than three years. The youngest and most undernourished children suffer the most severe complications and the highest risk of death. Diarrhea, malnutrition, pneumonia, and blindness associated with vitamin A deficiency are the worst complications. The infection is preventable by the timely administration of a potent vaccine. This endeavor requires a well-managed technical and administrative network that remains difficult to organize in many areas of the world. The vaccine is efficacious and has few adverse effects but must be provided to children during the short interval between loss of transplacentally acquired antibodies and the acquisition of natural infection. The improvements in heat stability of the vaccine increase the likelihood of providing potent vaccine, but a well-managed cold chain remains a prerequisite for any successful immunization program. Health education, improved management skills, publicity, and community support are all important factors for ultimately preventing the morbidity and mortality from this disease.