The frequency and determinants of cesarean section rates in Italy were analyzed using data collected routinely by the Italian Central Institute of Statistics on more than 2,400,000 deliveries in 1980-83. The rate of cesarean section in Italy rose from 11.2/100 deliveries in 1980 to 14.5 in 1983. This increase was comparable with other European countries, although the rate of abdominal deliveries was still about 30-40% lower than in the United States and Canada. In the southern (and less rich) areas, the rate of cesarean section was about 40% lower than in the North or Centre of Italy. The rate of cesarean birth rose constantly with maternal age; being in comparison with teen-agers, about three times higher in women aged 45 years or more. Compared with women with primary or intermediate degree, those with university education reported about 40% higher rate of cesarean section, but this differences was markedly reduced after taking into account maternal age and birth weight. In southern areas of the country the frequency of cesarean birth was about 40% higher in public hospital than in private ones (11.5 and 8.1/100 deliveries, respectively), while in northern and central areas the frequency of cesarean birth was higher in private hospital than public ones (18.5 vs 14.7/100 deliveries in the North, and 19.6 vs 14.6/100 deliveries in the Centre). There were relationships between cesarean rates and birth weight or gestational weeks. The lowest values were observed in very low birth weight (less than or equal to 999 gr) as in babies weighing 3000-3999 gr and in deliveries occurred between the 25th and 27th gestational weeks and in term deliveries. About 55% of deliveries with breech presentation were delivered by cesarean section.