Abstract Objectives To evaluate the efficacy and safety of 5 and 10mg doses of mifepristone for 6 months for the treatment of uterine fibroids and to check those results at 1 year post-treatment. Study design Randomised double-blind clinical study carried out at the “Eusebio Hernández” Hospital, Havana, Cuba. One hundred and seventy-six women with symptomatic uterine fibroids received one daily capsule of 10mg mifepristone orally or one daily capsule of 5mg mifepristone orally, over 6 months. Up to two endometrial biopsies were performed. Reduction in fibroid volume was used to evaluate efficacy. Results The 5 and 10mg dose had a similar efficacy in reducing the fibroid volume, 48.1% and 39.1%, p=0.07, and that of the uterus, 30.3% and 27.2%, p=0.63, respectively. Twelve months after treatment the majority of the subjects were asymptomatic with symptom prevalence similar to that at the end of treatment, except for hypermenorrhea and metrorrhagia, although the intensity of hypermenorrhea was much less, p<0.01. Conclusions (1) Both doses obtain similar results in reducing fibroid size. (2) Administering 6 months’ treatment achieves symptomatic improvement lasting 1 year in a high percentage of cases. (3) More studies need to be carried out with longer treatment and follow-up periods.