Background: Metastatic breast cancer is a common clinical entity, and its treatment is still a major clinical problem in modern oncology. Both cisplatin (CDDP) and 5-fluorouracil (5-FU) are effective agents. Patients and Methods: In this retrospective study, the therapeutic efficacy and tolerability of CDDP and continuous infusion of 5-FU were evaluated in patients with pretreated metastatic breast cancer. 16 patients were surveyed. All of them were pretreated with anthracyclines in an adjuvant and/or therapeutic setting. Eight of them also received taxanes after the failure of anthracyclines. CDDP at 80 mg/m(2) for 1 day and 5-FU at 1,000 mg/m(2) as a continuous 24-hour infusion for 5 consecutive days were administrated every 3 weeks. Results: 13 patients were included in response analysis. Because of severe toxicity, chemotherapy protocols of 3 patients were stopped after the first cycle. The objective response rate (partial response) was 46%. No complete response was observed. The median response duration was 5 (3.5-7) months in the response group. Favorable objective responses were observed more frequently in cases with skin metastasis. Five out of 6 patients who attained partial remission had skin metastasis. Response rates were similar in patients pretreated with taxanes and in those not pretreated with taxanes (75 vs. 80%). The most serious toxicity was myelosuppression (25%). Conclusions: Although this study is based on only a limited number of patients, the combination of CDDP and 5-FU can be recommended in patients refractory to both anthracyclines and taxanes and especially in cases of skin metastasis with a good performance status.