21 patients with metastatic breast cancer, refractory to conventional agents, were treated with a combination of BCNU, vincristine, mitomycin-C and prednisone given every 4 weeks. Only three of the nineteen (15.8%) evaluable patients were observed to have a partial remission, whereas four experienced stabilization of tumor. The sites which responded included skin lesions in two patients and a pleural effusion in 1 patient. This combination resulted in moderate to severe thrombocytopenia in five patients, but was otherwise well tolerated. This pilot study therefore suggests that these four agents in the schedule and doses given do not appear to be superior to any of these agents used singly for advanced, refractory breast cancer.