Our study of cesarean rates in 19 industrialized countries of Europe, North America, and the Pacific revealed sharp differences in rates, ranging from a low of 5 (Czechoslovakia) to a high of 18 (United States) per 100 hospital deliveries in 1981. Differences in cesarean rates according to maternal age, parity, and complications of pregnancy and childbirth reflected national differences in obstetrical practice. For example, the percentage of mothers who had a vaginal birth after a previous cesarean section was only 5 in the United States as compared with 43 in Norway, where the cesarean rate was half that in the United States. Despite the wide range of cesarean rates, almost all the countries studied have had consistent increases over the past decade, and the annual rate of increase for all countries appears to be converging. The steady pace of increase in developed countries, combined with comparable or even higher rates of cesarean delivery now being reported in less developed countries, underscores the need for the medical community to consider the appropriateness of this continued rise in the number of cesarean deliveries.