The changing annual vaccination status of the population and the greater than 1,000-fold drop in reported annual incidence of paralytic poliomyelitis between the early 1950s and early 1970s indicate that the control of poliomyelitis in the United States must be attributed to the use of both the inactivated poliovirus vaccine and oral poliovirus vaccine. The containment, in 1972 and 1979, of rare epidemics in poorly vaccinated subpopulations and the existence of only three reported cases of paralytic poliomyelitis clearly attributable to wild poliovirus in the last three years document a major triumph for public health. The continuing occurrence of vaccine-associated paralysis (six or seven reported cases per year, 1980-1982) indicates the necessity, despite the accomplishments, for continued review of the current vaccination strategy.