Objective: To determine whether the use of a prostaglandin (PG) E2 3-mg pessary followed by a delay of 12 hours before stimulation of labor with oxytocin improves obstetric outcome compared with the use of a placebo pessary. Methods: One hundred fifty-five nulliparas at term with poor cervical scores (modified Bishop score below 6 of 10) and premature rupture of membranes (PROM) were recruited for this double-blind, placebo-controlled randomized trial. On admission to the study, either a PGE2 pessary or an identical-appearing placebo pessary was inserted into the posterior fornix. If labor did not start in the next 12 hours or if symptoms and signs of infection were evident, labor was induced with oxytocin infusion. Assignment was unblinded at the end of the study, and details of the labor and maternal and neonatal outcome in women who received a PG pessary were compared with those who received a placebo pessary. Results: Women receiving a PG pessary were significantly less likely to require stimulation of labor at the end of 12 hours than were those given a placebo pessary (37 versus 58%, P = .002). The mean time between admission to study and delivery was significantly shorter in the PG group compared with the placebo group (15 versus 19 hours, P = .01). The rate of cesarean delivery was not statistically different in the two groups (13.9% with PG versus 15.8% with placebo). Conclusion: In nulliparas with poor cervical scores who present with PROM at term and no evidence of infection or obstetric complications, use of a PGE2 pessary resulted in more women establishing labor earlier, with a resultant reduction in the admission-to-delivery interval, compared with the use of a placebo pessary. The cesarean delivery rates in the two groups were similar, and there were no significant differences in neonatal outcome.