In a prospective study, 121 patients with spontaneous rupture of the membranes of greater than 6 hours duration and unfavourable Bishop-Score (less than 6) were stimulated with 3 mg vaginal prostaglandin-E2-tablets. All patients started labour. Only one patient had a hyperstimulation which was corrected with betamimetics. There were no systemic side effects. Almost 90% of the women delivered on the first day. The rate of the Caesarean sections was low. There was no case of intraamniotic infection; the foetal outcome was good. In conclusion, vaginal prostaglandin-E2-tablets are safe to use in spontaneous rupture of the membranes.