Using a randomized double-blind research design, the efficacy and safety of intravenous prostaglandin F2a(PF) and oxytocin (O) for inducing labor were compared in term pregnant women. The results show that successful induction depends upon the condition of the cervix, and for comparable groups there was no difference for PF or O. The PF failures occurred in patients who were significantly more obese. The incidence of uterine hypertonus, hot flashes and vein phlebitis was increased significantly in the PF group but there was no difference in the incidence of fetal bradycardia, nausea, vomiting or diarrhea. The infants delivered vaginally were of similar weight and had similar 1- and 5-minute Apgar scores. Laboratory toxicity studies, before and after infusions (complete blood count, uric acid, bilirubin, SGOT, and blood urea nitrogen), were similar for the two drug groups, except that hemoglobin levels postinfusion were significantly higher in the O group. The incidence of cesarean section was significantly increased in the PF group and these sections were done for uterine hypertonus and/or fetal bradycardia. Caution should be exercised before prostaglandin Fα solutions are used routinely to induce labor at term.