Objective: To compare two dosage regimens for the administration of vaginal prostaglandin gel in triacetin base for induction of labor. Methods: Seventy subjects planned for elective induction of labor at term were randomized to treatment with PGE, vaginal gel every 6 or 12 hours. The 6-hourly group received an initial dose of 1 mg, followed by 2 mg at 6 hour intervals for a maximum of two additional doses if not in active labor. The 12-hourly group had an initial dose of 2 mg followed by two additional doses at 12 hour intervals if not in active labor. Results: Successful induction rate was higher in the 12-hourly as compared to 6-hourly gel regimen (100% vs. 91%, P > 0.05). Twelve hours after the initial dose delivery occurred in34% of the 12-hourly group as compared to 20% of the 6-hourly regimen (P < 0.05) and by 18 hours delivery had occurred in 57% and 37% respectively (P < 0.01)． We found no d1fference in the induction-active labor interval (P > 0.05), and the induction-delivery interval (P > 0.05) between the two groups. Active labor followed a single dose of gel in 66% of the 12-hourly group com­pared to 40% of the 6-hourly group (P < 0.01). Syntocinon augmentation was needed in 6% of subjects in the 12-hourly group as compared to 26% in the 6-hourly group (P < 0.01). The cesa­rean section rate was similar in both groups. Uterine hyperstimulation occurred less frequently in the 12-hourly group (P < 0.05). The perinatal outcome was similar in both groups. Conclusions: The 12-hourly regimen was more effective than the 6-hourly regimen in initia­ting labor. The majority of the subjects in the 12 hourly group achieved labor following a single dose of gel. Induction delivery interval, however, was similar in both groups.