PURPOSE: to compare the effectiveness of the Foley balloon with vaginal misoprostol for cervical ripening and labor induction. METHODS: randomized clinical trial, not blind, conducted from January 2006 to January 2008. A total of 160 pregnant women with indication for induction of labor were included and divided into two groups, 80 for Foley and 80 for vaginal misoprostol. Inclusion criteria were: gestational age of 37 weeks or more, a live single fetus with cephalic presentation and a Bishop score of four or less. We excluded patients with a uterine scar, ruptured membranes, estimated fetal weight greater than 4000 g, placenta previa, chorioamnionitis and conditions that imposed the immediate termination of pregnancy. Statistical tests employed were Mann-Whitney, χ 2 test or Fisher's exact test, and p value was significant if less than 0.005. RESULTS: misoprostol triggered more frequently spontaneous delivery (50.0 versus 15.0% for Foley, p<0.001) and required less use of oxytocin (41.2 versus 76.2%), and this group presented more tachysystole (21.2 versus 5.0%). The Foley catheter caused more discomfort to the patient (28.7 versus 1.2%). There were no differences in the time required for development of the Bishop score (20.69 versus 21.36 hours), for triggering delivery (36.42 versus 29.57 hours) or in rates of cesarean delivery (51.2 versus 42.5%). There were no significant differences in perinatal performance, with similar rates of abnormal cardiotocography (20.0 versus 21.2%), presence of meconium (13.7 versus 17.5%) and need for neonatal intensive care unit (3.7 versus 6.2%). CONCLUSIONS: the use of the Foley catheter was as effective as misoprostol for cervical ripening, but less effective in triggering spontaneous labor. Our results support the recommendation of its use for cervical ripening, especially in patients with cesarean scar.