Pregnancy was successfully terminated in 8 of 9 patients 5 to 6 weeks after the last menstrual period by serial intramuscular injections of 15(S)-15-methyl-prostaglandin F2alpha (15-ME-PGF2alpha). In one patient the treatment induced vaginal bleeding and a drop in hormone levels, but the patient did not completely abort and the uterus had to be evacuated. Serial intramuscular injections of 15-ME-PGF2alpha appeared to have some luteolytic effect, resulting in a significant drop in progesterone and estradiol levels. However, it is uncertain if the luteolytic effect of the prostaglandin was the precipitating factor in the abortion since the administration of 15-ME-PFG2alpha was accompanied by strong uterine activity which played a role in the abortion.