Poliomyelitis lameness surveys in children of school age recently reported from Burma, Egypt, Ghana, and the Philippines have indicated an estimated, average annual endemic incidence of paralytic poliomyelitis similar to or higher than the overall average annual rate in the USA during the peak years in the prevaccine era. Contrary to oft-expressed dogma, high rates of paralytic poliomyelitis are occurring annually in regions with high infant mortality rates, continuing undernutrition, and absence of basic sanitary facilities. Recent data indicate that prolonged breast feeding does not impede the effectiveness of oral poliovirus vaccine (OPV). A high prevalence of nonpoliovirus enteric infections can modify, delay, and lower the frequency of seroconversion after OPV, but these effects are overcome by multiple doses. The problem of eliminating paralytic poliomyelitis from economically underdeveloped countries depends on administrative rather than immunological or epidemiological factors, although a specially concentrated effort is needed in countries where most of the cases occur during the first two years of life and where paralytic polioviruses are propagating throughout the year in a large proportion of the infant population. Under such circumstances, expanded routine infant immunization programmes, which include OPV but reach at best only 20-40% of the total infant population, who receive only one or a few doses of vaccines requiring multiple doses, cannot be expected to eliminate paralytic poliomyelitis as an important public health problem. Injections of multiple doses of quadruple vaccine (DPT + inactivated poliomyelitis vaccine) would not only greatly increase the cost of routine immunizations but would not achieve more or as much as feeding OPV at the time of the DPT injections. Mass administration of OPV each year on 2 days of the year 2 months apart, to all children under 2, 3, or 4 years of age (depending on the epidemiological situation), without reference to the number of OPV doses they may have had before, can be expected to yield optimum results in countries with small numbers of professional health personnel and many other year-round problems.