A new tissue-selective prostaglandin E2-derivate, 16-Phenoxy-prostaglandin E2-methansulfonamide (SH B 286) developed by Pfizer, USA, and Schering, Germany, has been investigated as abortifacient using the intrauterine as well as intravenous route of application. Vital signs, intrauterine pressure, serum levels of steroid hormones, hPL and hCG were recorded before, during and after administration of Pg SH B 286. By using 100--250 microgram Pg SH 286 extraamniotically abortion rates reached 80%. Severe systemic effects did not occur. Uterine cramps (40% of the women), nausea (23%) and vomitus (15%) were tolerable and needed rarely medication. The intravenous administration of Pg SH B 286 has been investigated for the first time with three dosis regimens. 33 of 38 women had complete abortion with dose-dependant side effects and without severe complications. The low dosage schedule (0,5--1,5 microgram/ml, total approx. 1000 microgram) had the same efficacy rate as the higher ones and was associated with the lowest systemic side effects. Premedication with analgetics was not necessary. Pg SH B 286 caused a marked increase of intrauterine pressure inducing abortion. If the measured decline of steroid hormones--mainly progesterone--contributes to the abortifacient efficacy of this prostaglandin is yet unsolved. The clinical usefulness of Pg SH B 286 has been demonstrated by our study.