OBJECTIVE: To estimate the effect of outpatient administration of a single d os e of vaginal misoprostol at term on the interval to delivery in women with unfav orable cervices. METHODS: Randomized, double blind, placebo-controlled trial co mparing a single 25-μg outpatient intravaginal dose of misoprostol to placebo in pregnant women with Bishop scores less than 9 at 40 weeks or greater. After p lacement of the study medication, subjects were permitted to go into spontaneous labor unless an indication for induction developed. Analysis was by intent to t reat. The interval to delivery, defined as the time from medication placement to delivery, was compared by Student t test and by survival analysis with the log -rank test. RESULTS: Thirty-three women were randomly assigned to receive miso prostol, and 35 were assigned to receive placebo. The mean interval to delivery was significantly less in the misoprostol group, 4.2 ±.4.1 compared with 6.1 ± .3.6 days, P = .04. The interval to delivery for only the nulliparous patients w as significantly less in the misoprostol group, 4.2 ±.4.0 compared with 7.2 ±. 3.7 days, P = .02. The survival curves for the interval to delivery were signifi cantly different (P = .04 by log-rank test) with 4.1 days median interval to de livery for misoprostol compared with 9.2 days for placebo. There were no adverse outcomes in either group. CONCLUSION: A single 25-μg outpatient intravaginal dose of misoprostol is effective in decreasing the interval to delivery in women with unfavorable cervices at term. OBJECTIVE: To estimate the effect of outpatient administration of a single d os e of vaginal misoprostol at term on the interval to delivery in women with unfavorable cervices. METHODS: Randomized, double blind, placebo-controlled trial co mparing a single 25-μg outpatient intravaginal dose of misoprostol to placebo in pregnant women with Bishop scores less than 9 at 40 weeks or greater. After p lacement of the study medication, subjects were permitted to go into spontaneous labor unless an indication for induction developed. Analysis was by intent to The interval to delivery, defined as the time from medication to delivery, was compared by Student t test and by survival analysis with the log-rank test. RESULTS: Thirty-three women were randomly assigned to receive miso prostol, and 35 were assigned to receive placebo. The mean interval to delivery was significantly less in the misoprostol group, 4.2 ± .4.1 compared with 6.1 ± .3.6 days, P = .04. The interval to de livery for only the nulliparous patients w less significantly in the misoprostol group, 4.2 ± .4.0 compared with 7.2 ±. 3.7 days, P = .02. The survival curves for the interval to delivery interval of signifiantly cantly different (P = .04 by log-rank test with 4.1 days median interval to livery for misoprostol compared with 9.2 days for placebo. There were no adverse outcomes in either group. CONCLUSION: A single 25-μg outpatient intravaginal dose of misoprostol is effective in decreasing the interval to delivery in women with unfavorable cervices at term.