The purpose of this study was to compare prevalence of cesarean sections in nine private maternity hospitals in the city of Rio de Janeiro in 1968 and 1993, seeking to correlate the form of payment with prevalence of cesareans. We analyzed 3,413 deliveries in 1968 in nine maternity hospitals, at a time when a form of payment called "per service unit" was used. Twenty-five years later, these same maternity hospitals were reanalyzed, with a total of 11,065 births. These data were from Gentile de Mello (1968) and the Report from the Information System on Live Births, by the Rio de janeiro Municipal Health Secretariat. We performed a statistical analysis on the proportion of cesareans comparing the two years and observed a statistically significant increase in their prevalence in 1993 as compared to 1968, although payment was nearly equal for childbirth care in the two years. The elimination of the "per service unit" payment system and the implementation of equal payment for transvaginal and cesarean deliveries proved insufficient to decrease the prevalence of cesareans. We suggest that form of payment alone does not determine the high prevalence of cesarean sections, and that other variables are impacting this phenomenon.