Poliomyelitis appeared in Cuba in the present century and acquired an endemo-epidemic character, with epidemic peaks every five to seven years. The first polio vaccination campaign, conducted in 1962, changed the trend of the disease by eliminating the morbidity and mortality peaks. Since that time there have been only isolated cases. There have been 21 mass vaccination campaigns, which have been preceded by serologic studies on a sample of the national population younger than 14 years of age. Since the eighth campaign, a trivalent vaccine candy has been administered in two doses to children from one month to three years of age. A booster dose at nine years of age was introduced in the ninth campaign. Since 1962, seven cases have been reported in infants younger than one year of age who, for various reasons, had not been vaccinated. The key to the success of the mass vaccination campaigns conducted over the last 20 years has been the use of the Committees for the Defense of the Revolution. The high vaccination coverage achieved in the various campaigns for each age group (>80%) guarantees that no epidemics will break out in the country. Quality-control surveys following each vaccination operation have yielded an understanding of difficulties and have allowed measures to be taken to improve operations.