A new prostaglandin E2 derivative (Sulprostone) was given extra-amniotically to 17 healthy women, who were 7-8 weeks pregnant, in order to assess the plasma profile of HCG, 17 beta-estradiol (E2), and progesterone and to evaluate the effectiveness and overall acceptability of the method in relation to different dose levels. On the lowest dose level (5 micrograms) only 3 of 7 patients aborted within a 3-to 6-day period. At higher dose levels (10 and 15 micrograms, respectively) 9 out of 10 women exhibited clinical evidence of an abortion. In the group who aborted, E2, progesterone, and HCG decreased continuously, whereas in the nonabortion group decreased levels were found 3 and 6 h after administration of the drug, but already after 24 h the values had again increased. Practically all treated women experienced lower abdominal discomfort, 7 (41%) reported the pains being severe. Vomiting and/or diarrhea occurred in 4 patients (24%). Similarly to other hitherto tested prostaglandins in humans, this new analogue exhibits its effect primarily through direct stimulatory effect on the uterine smooth muscle, resulting in subsequent decline in the concentrations of HCG, E2, and progesterone. In the group of successful inductions the decrease of the HCG concentration was close the half-time of HCG, indicating a permanent damage to the placenta. Despite the high success rate at a dose of 10 micrograms or more, the side effects, mainly abdominal cramps. were too severe to make this method feasible for the induction of early abortion when comparing to the available routine procedure of rapid vacuum curettage used on an outpatients basis.