64 eligible women with previously treated metastatic breast cancer received mitomycin C plus vindesine chemotherapy. Dosage was based on investigators' estimate of patients' bone marrow reserve. There were 19 evaluable patients in the good marrow reserve category, with two complete and three partial responses (26%). In the poor marrow reserve category there were 29 evaluable patients with four partial responses (14%). The 26% response rate in patients with good marrow reserve is consistent with results obtained with this and similar combinations by other investigators.