OBJECTIVE To determine if outpatient cervical ripening using misoprostol can initiate labor within 48 hours of medication administration and to determine if time from medication administration to time of delivery is decreased using outpatient cervical ripening. METHODS Uncomplicated singleton, vertex pregnancies at 41 weeks' gestation or later with Bishop score of 4 or less were eligible for enrollment. Other inclusion criteria included intact membranes, less than eight uterine contractions per hour, a reactive nonstress test, and amniotic fluid index (AFI) over 5 cm. After randomization, 25 micro(cg) of misoprostol or placebo was placed within the posterior vaginal fornix. Patients were continuously monitored for 4 hours, then discharged if not in active labor. Patients returned in 24 hours for a repeat administration of the respective medication. Patients not delivered within 48 hours were admitted for inpatient induction of labor. Statistical analysis was performed with the Fisher, Student t, chi(2), and Mann-Whitney U tests, with P <.05 considered statistically significant. RESULTS Among the 60 patients enrolled, 27 (45%) received misoprostol and 33 (55%) received placebo. The majority (24 of 27, 88.9%) of study group patients entered active labor within 48 hours after dosing, compared with 16.7% (five of 33) of placebo group patients (P <.001). The time from initial dose to delivery was significantly shorter in the misoprostol group (36.9 +/- 3.8 compared with 61.3 +/- 3.8 hours, P <.001). CONCLUSIONS Intravaginal misoprostol is effective for outpatient cervical ripening. No adverse effects were encountered, although further study is required to determine the safety of this treatment regimen.