Objective: To assess the safety and efficacy of a protocol that mandated at least 12 hours of oxytocin administration after membrane rupture before cesarean delivery for failed labor induction in the latent phase. Methods: Gravidas at or beyond 36 weeks' gestation undergoing indicated induction with cervical dilatation up to 2 cm were studied prospectively. Prior cesarean was an exclusion criterion. If the fetal heart rate pattern was reassuring, cesarean was not permitted before the active phase of labor (4-cm dilatation and at least 90% effacement or 5-cm dilatation regardless of effacement) unless the membranes had been ruptured and oxytocin administered for at least 12 hours. Results: Five hundred nine women were treated according to protocol; 360 (71%) were nulliparas and 149 (29%) were parous. Twenty-five percent of nulliparas and 9% of parous women were delivered by cesarean. After 6 hours of ruptured membranes and oxytocin, 14% of nulliparas were still in the latent phase; 39% of whom delivered vaginally, compared with 7% still in the latent phase after 9 hours (vaginal delivery rate 28%), and 4% after 12 hours (vaginal delivery rate 13%). In contrast, after 6 hours of ruptured membranes and oxytocin, only five (3%) parous women were still in the latent phase. Among those, none remained in the latent phase for 12 hours and all were delivered vaginally. No women had serious complications. Severe neonatal morbidities were infrequent and not related to duration of the latent phase. Conclusion: By requiring a minimum of 12 hours of oxytocin after membrane rupture before failed labor induction could be diagnosed, many nulliparas who remained in the latent phase at 6 and 9 hours had safe vaginal deliveries, and failed labor induction was eliminated as an indication for cesarean in parous women. (C) 2000 by The American College of Obstetricians and Gynecologists.