Resumen:
Costa Rica has undergone a dramatic reduction in its infant mortality rate from 68 per 1,000 live births in 1970 to 20 per 1,000 in 1980. In the present study, changes during this century, mortality differentials, and causes of death are analyzed, and multiple regression techniques are used to identify the determinants of the decline in Costa Rica's 79 cantons (counties). Although socioeconomic development and greatly reduced fertility contributed to the infant mortality decline, as much as three-fourths of the decline is attributable to public health programs implemented during the 1970s. The extension of primary health care—especially rural and community programs—seems to be responsible for 40 percent of the reduction. In addition, health services produced a notable decrease in the socioeconomic differentials related to children's risk of death. The unique achievements o f this developing country offer a new strategy for public health improvement.