[Factors associated with cesarean section rates in a university hospital]. 
To assess factors associated to cesarean section.  A cross-sectional study was conducted in a university hospital in Florianópolis, Southern Brazil, from 2001 to 2005.  Socioeconomic, reproductive, obstetric and institutional information were collected.  Data from 7,249 deliveries was obtained from medical records and admission, delivery and post-delivery records.  Cox regression was used in the analysis to estimate cesarean prevalence ratios in the categories of variables studied.  Cesarean rates increased from 27.5% to 36.5% during the period studied and they were higher than those associated with medical indications.  After adjustment for confounders cesarean rates were positively associated with previous cesarean section (PR=2.65, 95% CI: 2.31;3.05), non-cephalic presentation (PR=2.23, 95%CI: 1.69;2.95), oxytocin use (PR=1.77, 95%CI: 1.43;2.19), dilatation at admission (PR=2.74, 95%CI: 2.18;3.44), and obstetrician profile (>35% of cesarean sections) (PR=1.82, 95%CI: 1.36;2.42).  The factors associated with cesarean section indicate the need of interventions focusing on women and their reproductive experience and changes in obstetrician practice as well.