A double-blind study evaluating two dose schedules of oral prostaglandin E2(PGE2) was conducted in 56 normal “unripe” multiparas at term. The effect of PGE2was evaluated by comparing the change in Bishop score of the cervix and patient's response to oxytocin induction of labor after the prostaglandin priming. In the two study groups (one group on a fixed PGE2dosage and the other on a variable drug regimen) an average change of more than three points in the Bishop score was observed. In the control group no significant change in cervical ripeness was observed. Nine of the 32 patients (28%) receiving prostaglandin delivered during the priming phase of the study, whereas only 1 control patient (4.2%) delivered during priming. Six of 24 control patients (25%) failed to deliver, whereas only 3 of 32 study patients (9%) failed. In the successfully induced patients, the response to oxytocin, as expressed by the time to active phase, total time of labor, and mean dose of oxytocin required, did not vary significantly when control and study groups were compared. It is concluded that PGE2at either dosage schedule is effective in changing the Bishop score of the cervix and that it is not feasible to titrate the PGE2dose in order to effectively ripen the cervix without a very high incidence of induction of labor. In those cases where priming was completed, without accidental deliver)', the induction phase was successful more than 90% of the time. No adverse effect to mother or baby was observed during this study.