In a randomized double-blind study we evaluated the effects on cervical ripening and labor induction of 0.5 mg PGE2 in gel given intracervically and 2.0 mg PGE2 given as a vaginal suppository. All patients were at term with unfavorable cervical scores. The indications for induction were toxemia, diabetes mellitus, Rh-immunization, or intrauterine growth retardation. Significantly better results for both cervical priming and labor induction were obtained after intracervical PGE2-gel application than after treatment with placebo or vaginal suppositories. Eleven out of 19 patients (58%) were delivered within 24 h after intracervical PGE2-gel compared to two out of 19 patients given placebo (p less than 0.01). In patients not delivered 24 h after the start of treatment, the mean cervical score had changed from 3.7 to 6.0 (p less than 0.05) after PGE2-gel application compared to a change from 3.9 to 4.3 after placebo treatment (n.s.). The outcome after treatment with PGE2 suppositories did not differ significantly from that with placebo treatment. In a subsequent study 25 patients were given 0.5 mg PGE2-gel intracervically. The results were consistent with those obtained in patients receiving PGE2-gel intracervically in the double-blind study. Few side effects were noted. No patient complained of gastro-intestinal discomfort but increased myometrial activity was observed in two patients; one after placebo and the other after active intracervical PGE2-gel treatment. The hyperactivity was readily countered with the beta 2-agonist, terbutaline. All infants were born in good condition with Apgar scores of 7 or more within 5 min. At pediatric examinations at 1 week and at 6 months of age all children seemed healthy.