The aim of this study was to investigate the prevalence of caesarean section in the Islamic Republic of Iran in different provinces and to compare the sociodemographic characteristics of married women with and without caesarean section. Data were analysed from the Iranian Demographic and Health Survey of a representative sample of married women (n = 17,991) who delivered a baby between September 1998 and October 2000. Overall, 35.0% of deliveries were by caesarean section. Women having a caesarean section were older, better educated, married at a later age and with lower parity than those who delivered normally. Provincial variations in rates were significantly correlated with indices of socioeconomic development.