The purpose of this study was to compare the efficacy of misoprostol that is administered in the buccal pouch with the intravaginal route of administration.One hundred fifty-seven pregnant women with a singleton live gestation, Bishop score of 24 weeks were randomized to receive misoprostol that would be placed either in the buccal pouch or vagina every 6 hours. In the buccal group, after the first 2 doses of 200 microg, the dose was increased to 300 microg for the duration of the study (up to a total of 1600 microg). In the vaginal group, after the first 2 doses of 50 microg, the dose was increased to 100 microg for the duration of the study (up to a total of 500 microg). The primary outcome variable was the interval from the first dose to vaginal delivery. Power calculations indicated the need to enroll 71 patients in each arm of the study, which would allow for the detection of a 4-hour reduction in vaginal birth interval for buccal misoprostol.The hours from drug administration to vaginal delivery were similar between the buccal and vaginal groups (23.5 +/- 20.8 hours versus 21.3 +/- 13.4 hours), respectively. Thirty-five women (63%) versus 34 women (67%) delivered vaginally within 24 hours (P = not significant). The incidence of tachysystole was higher in the buccal group, 28 occurrences (38%) versus 15 occurrences (19%; P =.01).Buccal misoprostol is effective for cervical ripening but results in a higher incidence of tachysystole than does intravaginal administration.