OBJECTIVE: To identify factors driving the rapid increase in caesarean section in China between 1988 and 2008. METHODS: Data from four national cross-sectional surveys (1993, 1998, 2003 and 2008) and modified Poisson regression were used to determine whether changes in household income, access to health insurance or women's education accounted for the rise in caesarean sections in urban and rural areas. FINDINGS: In 2008, 64.1% of urban women and 11.3% of women in the poorest rural region reported giving birth by caesarean section. A fast rise was occurring in all socioeconomic groups. Between 1993 and 2008, the risk of caesarean section had increased more than threefold in urban areas (relative risk, RR: 3.63; 95% confidence interval, CI: 2.61-5.04) and more than 15-fold in rural areas (RR: 15.46; 95% CI: 10.46-22.86). After adjustment for improvements in income, education and access to health insurance over the study period, the RR dropped minimally in urban areas (RR: 3.07; 95% CI: 2.32-4.07), which suggests that these factors do not explain the rise; in rural areas, the adjusted RR dropped to 7.18 (95% CI: 4.82-10.69), which shows that socioeconomic change is only partly responsible for the rise. Socioeconomic region of residence was a more important driver of the caesarean section rate than individual socioeconomic status. CONCLUSION: The large variation in caesarean section rate by socioeconomic region--independent of individual income, health insurance or education--suggests that structural factors related to service supply have influenced the increasing rate more than a woman's ability to pay.