To compare the efficacy of antiprogesterone (mifepristone) in combination with a synthetic prostaglandin E1 analogue (misoprostol) for outpatient treatment of miscarriages. One hundred and twenty-two women with first trimester miscarriages. The women were randomised to treatment with mifepristone 400 mg orally followed by a single oral dose of 400 microg misoprostol 48 hours later (n = 60) or expectant management (n = 62). Women were re-evaluated five days later. If retained intrauterine products of conception were found with an antero-posterior diameter above 15 mm on transvaginal ultrasound, surgical evacuation was performed. Eighty-two percent of the women randomised to pharmacological treatment and 76% of those randomised to expectant management had an empty uterine cavity after five days. Convalescence time was 1.8 days longer for women randomised to pharmacological treatment. Pain, bleeding, complications, and satisfaction with the treatment did not differ between the groups. Most cases of spontaneous incomplete miscarriage will become a complete miscarriage without intervention. This study shows that outpatient treatment with a combination of antiprogesterone and a prostaglandin E1 analogue did not increase the rate of complete miscarriage, compared with expectancy alone, by a clinical important degree.