Forty-two patients with metastatic breast cancer refractory to first-line therapies were treated with combination chemotherapy with mitomycin-C and vinblastine. A response to treatment was observed in 11 of 34 evaluable patients (32.3%), with 3 complete remissions (8.8%) and 8 partial remissions (23.5%). The median duration of response was 185+ days. The 12-month survival was 78% for responders, 48% for patients with stable disease and 0% for patients with progressive disease. The toxicity was acceptable with 20 episodes of moderate myelosuppression (58.8%) and 2 cases with congestive heart failure that responded to medical treatment. The MMC-VBL combination is an active regime for advanced breast cancer previously treated with antracyclines. This combination may be regarded as a standard second-line treatment for this type of tumor.