BACKGROUND: Uterine leiomyomas are widely prevalent and frequently cause menorrhagia. The major therapeutic option today is hysterectomy. Medical options are of highest interest. METHODS: A total of 30 women with uterine leiomyomas scheduled for surgical intervention were randomized to receive either 50 mg mifepristone or placebo every other day during 3 months prior to surgery. Uterine blood flow and leiomyoma volume were evaluated once a month until surgery. Endometrial biopsies were obtained prior to and at end of treatment. Relevant biochemistry, symptoms and bleeding were recorded. Primary outcome was reduction in uterine leiomyoma size. RESULTS: There was a significant percentual decrease (P = 0.021) in the total leiomyoma volume in the mifepristone-treated group, -28 (-48, -8) % (mean +/- 0, 95 confidence interval), compared with the control group values 6 (-13, 25) %. Mifepristone treatment significantly reduced the bleeding days (P = 0.001) and increased serum haemoglobin values (P = 0.046). Serum cortisol levels remained unchanged, while a mild increase in serum androgens was noted. Endometrial biopsies showed no premalignant changes or changes in mitotic indices. CONCLUSION: Mifepristone may offer an effective treatment option for women with uterine leiomyoma and the associated pronounced uterovaginal bleeding. Clinical Trials identifier: www.clinicaltrials.gov: NCT00579475.