A study was undertaken to determine whether the combination of oral tamoxifen and moistened misoprostol administered vaginally was superior to that of placebo and moistened misoprostol administered vaginally for elective termination of early pregnancies. A clinical trial was conducted with a study group of 150 healthy women with pregnancies of less than or equal to 56 days gestational age who desired pregnancy termination. Subjects were randomized to ingest either 20 mg of tamoxifen (group 1) or placebo (group 2) twice daily for 1 day, followed 48 h later by vaginal administration of 800 mu g of saline-moistened misoprostol. This dose of misoprostol was repeated 24 h later and 8 days later if an abortion had not occurred. The main outcome measures were incidence of complete abortion, hemoglobin levels, duration of vaginal bleeding, and incidence of side effects. Complete abortion occurred in 709 (93.3%) in group 1 and 68 (90.7%) in group 2. There were no differences in either group between earlier (less than or equal to 49 days) and later (50-56 days) gestations. The mean duration of uterine bleeding was 7.9 days and 8.2 days in group 1 and group 2, respectively. In group 1, 94.3% who aborted bled for <14 days, and in group 2, 95.6%. No subject required a blood transfusion. There were no significant differences in side effects between the two groups. These data suggest that pretreatment with tamoxifen is not necessary when using moistened vaginal misoprostol for abortion of pregnancies of less than or equal to 56 days of gestation. CONTRACEPTION 2000,60:353-356 (C) 2000 Elsevier Science Inc. All lights reserved.