First trimester legal abortions were induced in 20 patients by i.m. injection of a single dose of 1,000, 1,200 or 1,500 μg of sulprostone. Complete expulsion of the conceptus within 24 h occurred in 16 of the women. There was a tendency to a higher rate of complete expulsion, as well as gastrointestinal side effects, at higher dosages. No association was found between the completeness of expulsion and the patients’ serum progesterone levels before or after sulprostone injection.