This study evaluated the effectiveness of a single dose of the abortifacient effect of vaginal misoprostol followed by prolonged observation. Women with < or =42 days of amenorrhea, pregnancy confirmed by ultrasound, and approved request for termination received 800 microg of vaginal misoprostol once and were observed for 1 week. The gestational sac was measured before misoprostol administration, and 24 h and 7 days afterward. Women reported bleeding, expulsion of sac, and other complaints. After 1 week, those who had not aborted received a second dose of 800 microg. Those who had not aborted by 24 h later were treated by vacuum aspiration of the endometrial cavity. Twenty-four hours after treatment, 71.8% had aborted, and 87.1% aborted 3 days after treatment. After the second dose, 7 days later, the cumulative abortion rate reached 92.1%. None of the subjects who aborted required curettage or vacuum aspiration. The main complaints were pain (84.5%), nausea (21.4%), and headache (17.5%). No clinical differences between responders and nonresponders was found. Vaginal misoprostol, 800 microg, is effective in inducing early termination of pregnancy, and there is no need for an additional dose within 72 h after the first administration of misoprostol.