To identify factors associated with cesarean section in women with only one previous delivery by cesarean section and undergoing a trial of labor. A retrospective cross sectional study was performed from 1986 to 1998 including a total of 1746 women with one prior cesarean section and delivering after a trial of labor. Cases with a current twin pregnancy or with malformation incompatible with life were excluded. Women were divided in two groups according to the mode of the second delivery: Cesarean (n=731) or Vaginal Birth After Cesarean (VBAC, n=1015). To identify factors associated to the mode of delivery, the prevalence ratios (PR) and the 95%CI for each isolated factor, adjusted according to age, were assessed. In each analysis, cases with missing information were excluded. The total rate of Vaginal Birth After Cesarean was 58.1%. The factors significantly associated with cesarean section were: higher maternal age, greater fundal height (PR 1.5; 95%CI 1.19-1.88), premature rupture of membranes (1.3; 1.08-1.54), amniotic fluid with an altered aspect (1.22; 1.04-1.43) or volume (1.32; 1.01-1.73), altered fetal heart rate (1.96; 1.68-2.28), non cephalic presentation (2.03; 1.54-2.66), induction of labor (1.74; 1.42-2.11) and no labor analgesia (2.57; 2.11-3.11). The factors associated with cesarean section were older age, non-cephalic presentation, premature rupture of membranes, signs of large fetus, the need of induction of labor and signs of compromised fetal wellbeing.53109-15