We assessed antitumor activity and toxic effects of cisplatin and 5-day continuous infusion vinblastine in 25 evaluable patients with metastatic breast carcinoma refractory to one or more chemotherapeutic regimens. We administered cisplatin at 70 mg/m2 i.v. followed by vinblastine 1.5 mg/m2 daily for five consecutive days. In our heavily pretreated, poor performance patient population, we observed one complete response and four partial responses, with a median time to progression of 35 weeks. Toxic effects were significant and prevented dosage escalation. The addition of cisplatin does not appear to improve the therapeutic value of vinblastine alone.