A randomized controlled trial was made to compare the therapeutic result of oral high-dose medroxyprogesterone acetate (HD-MPA) versus mepitiostane (MS) in the treatment of postmenopausal breast cancer. MPA (1200 mg) was given p.o., b.i.d. to 47 patients and produced objective response in 19 of them (40.4%). Objective response was seen in 14 of the 40 control patients given MS p.o., b.i.d. (35.0%). Among patients with bone metastases, 6/19 (31.6%) for HD-MPA and 2/23 (15.4%) for MS showed objective response. The other merits of HD-MPA suggested in the study were improvement in performance status, anabolic effect and myeloprotective effect.