Forty early pregnancies (menses delay 13 - 27 days) were terminated by administering four vaginal suppositoreis each containing 1.0 or 1.5 mg of 15 (S) 15-methyl-prostaglandin F2alpha-methyl ester, one every third hour. In 14 cases serial measurementsof serum estradiol and progesterone were performed during and after therapy. Uterine contractions and bleeding started 1 - 17 hours after administration of the first suppository. Abortion was complete after one week in five women (13%), and after two weeks in 30 (75%). A curettage was performed on eight women, residual placental fragments were found in seven and pregnancy continued in one woman. Mild diarrhoea (65%) and vomiting (40%) were the major side-effects, despite premedication. Estradiol and progesterone levels fell progressively during the therapy. Self-administration of 4 or 6 mg of the methyl ester caused too low a rate of complete abortion for use in practice, but it may be a valuable and practical agent for preoperative dilation of the cervix.