Delivery with an unfavorable cervix using oxytocin is frequently unsuccessful. Used widely in Europe and increasingly in this country, locally applied prostaglandin E2 appears to improve labor induction. The present study prospectively evaluated the efficacy and safety of a prostaglandin gel (0.5 mg) placed intracervically. The use of the gel, when compared to a control group who received no pretreatment prior to labor induction, resulted in improved Bishop scores (7.5 +/- 1.0 vs. 1.8 +/- 0.3, P less than 0.0001), reduced induction to delivery intervals (10.1 +/- 2.1 vs. 20.6 +/- 2.0 hours), reduced oxytocin infusion duration (10.0 +/- 2.1 vs. 20.0 +/- 2.3 hours. P less than 0.0001) resulting in a lower cesarean delivery rate, 26 vs. 47 per cent (P greater than 0.05). Thirty-two per cent of patients receiving the prostaglandin gel labored and delivered within 12 hours and required no oxytocin. In addition, the use of prostaglandin E2 gel appeared safe in that no patient experienced an untoward reaction. Two cases of uterine hyperstimulation occurred that required uterine tocolysis but were not associated with fetal distress. The use of prostaglandin gel appears to be a safe and effective method to improve cervical inducibility in patients undergoing induction for a variety of maternal and fetal indications.