This study was undertaken to determine the effectiveness of prostaglandin E2 as a means for priming the cervix. Preparatory to induction of labor at 3rd trimester in 27 patients with unfavorable Bishop score of less than 6, an interval of priming was followed 6 hours by induction with oxytocin infusion. In the control group, only oxytocin was performed in patients in which cases Bishop score was less than at 3rd trimeser. It was concluded tat PGE2 was effective in changing Bishop score of the cervix. Six hours after last priming dose PGE2 Bishop score was increased 4.3 in primiparas and 5.4 in multiparas. The mean induction delivery interval was shorted about 20 hours in primiparas and about 15 hours in multiparas than control group. Especilly in the pregnancy induced hypertensive groups, the cervical change after priming by PGE2 was much improved and mean induction delivery interval was shortened over 10hours than control group in both primiparas and multiparas.