Twenty-six postmenopausal consecutive patients with advanced breast cancer were treated with very high medroxyprogesterone acetate doses (4000 mg/day orally for 30 days and then 3000 mg/day orally until progression or intolerance). The dominant metastatic lesion was bone in 13 patients, soft tissue in 3 patients and viscera in 10 patients (C.I. = V/ST + 0 = 0.62). An objective partial remission was achieved in 16 pts (61%), no change in 8 (31%), progression in 2 (8%). The median duration of objective remission was 7.5+ months with a median survival of 14.5+ months in responders. Toxicity was minor and only two patients discontinued the treatment because of side-effects. These results confirm the utility of medroxyprogesterone acetate at very high doses in these patients and the feasibility of this kind of dose.