Attempt to induce labour with PGF2alpha was made for various indications in 22 primiparous and 27 multiparous patients being between the 35th and 44th weeks of pregnancy. Intravenous infusion of PGF2alpha was started with 3 mug/min. and increased in steps of 3 mug/min. at intervals of about one hour until labour-like contractions were recorded. This dose level was then maintained until delivery. Uterine activity and fetal heart rate was monitored prior to and throughout the infusion. The clinical condition of the newborns was also assessed by Apgar score and by physical examination one and four days after delivery. Labour was successfully induced with total doses ranging between 0.4 and 8.4 mg. In 88 per cent of the cases this resulted in vaginal deliveries within 2 to 12 hours. The latter part of the first stage as well as the second stage were remarkably short. Uterine hypertonus was observed in five cases (10%). Other types of abnormal uterine contractility patterns were fairly common. These were, however, not associated with pathological FHR changes except in one case where severe late decelerations were observed following marked uterine hyperactivity. The condition of the newborns was generally good and maternal side effects were very rare. PGF2alpha seems particularly valuable in cases of pre-term inductions where low Bishop scores are present but the risk of overstimulation demands careful supervision, if possible with cardiotochographic monitoring.