Vaginal administration of 15-ME-PGF2a suppositories successfully terminated pregnancy, as determined by a negative pregnancy test at 14 days following insertion, in 34 of 39 patients with gestations of 34 to 51 days of amenorrhea. Fifteen of 20 patients who received a single long-acting 3-mg suppository had negative pregnancy tests at follow-up, while all 19 patients in whom the 3-mg suppository was preceded by a rapidly acting 1-mg suppository successfully aborted. This two-suppository regimen resulted in a more rapid onset of uterine activity and vaginal bleeding, as well as a slight decrease in gastrointestinal side effects. Peripheral plasma levels of 15-ME-PGF2a as detected by radioimmunoassay were also more consistent with two suppositories. It appeared that the rapidly acting 1-mg suppository provided a "prostaglandin impact" which significantly enhanced the abortifacient effectiveness of the technique. Nine patients on the 2-suppository regimen had the procedure performed on an outpatient basis. Expanded studies are indicated to determine the practicality of this technique as a valid pharmacologic alternative to surgical interruption of very early pregnancy.