To determine the practicability of administering 15(S)-15-methyl-prostaglandin F2alpha-tromethamine (15(S)-15-Me-PGF2alpha) intra-amniotically for the induction of midtrimester abortion, initially 2.5 mg. of 15(S)-15-Me-PGF2alpha was administered to 20 physically healthy gravid women, and was repeated after 24 hours in those patients who had not aborted. Within 24 hours, 65% aborted, and within 36 hours, 95% aborted. Although 67% experienced emesis, no serious complications occurred. This abortion rate is similar to that obtained with the recommended dose schedule of the dosage of prostaglandin F2alpha approved by the Food and Drug Administration and those reported with intra-amniotic administration of either hypertonic saline or urea when augmented with high, continuous, intravenous infusions of oxytocin. While the study intra-amniotic dose schedule appeared to be practicable, large, comparative studies will be necessary to determine the most satisfactory dose schedule and whether this method is more acceptable than other available methods.