A prospective trial was conducted including 300 pregant women seeking elective abortion to evaluate the safety and efficacy of methotrexate and misoprostol for abortion at less than or equal to 56 days gestation. Subjects received methotrexate 50 mg/m(2) intramuscularly followed 7 days later by misoprostol 800 lug vaginally. The misoprostol dose was repeated the next day if the abortion did not occur. Outcome measures included successful abortion (complete abortion without requiring a surgical procedure), duration of vaginal bleeding, and side effects. Complete abortion occurred in 263/300 (87.7%, 95% CI 83.4, 91.2%) patients. The complete abortion rate was higher for early gestations: 183/202 (90.6%, 95% CI 85.7, 94.2%) at less than or equal to 49 days gestation, and 80/98 (81.6%, 95% CI 72.5, 88.7%) from 50-56 days gestation (p=0.038). Abortion occurred in the 24 hours following the initial or repeat misoprostol dose (immediate success) in 65.0%; the remaining 22.7% of women who aborted did so after a delay of 23.6 +/- 9.1 (mean +/- standard deviation) days. Vaginal bleeding lasted 14 +/- 7 days and 11 +/- 9 days in immediate success and delayed success patients, respectively. Overall, 69.7%, 87.7%, and 91.7% of patients had passed the pregnancy by 24, 28, and 35 days, respectively, after receiving methotrexate. Methotrexate and misoprostol side effects were minimal. This treatment regimen offers an alternative to surgical abortion or the use of antiprogestins and prostaglandin for medical abortion.