A total of 60 patients with advanced breast cancer were treated with a combination of prednimustine (P: 110 mg/m2, days 1-5), mitoxantrone (M: 12 mg/m2, day 1) and 5-fluorouracil (F: 500 mg/m2, day 1) (PMF). Treatment was repeated every 3 weeks. In all 53 patients were evaluable for response. A total of 12 subjects had failed prior chemotherapy for metastatic disease. In response to PMF treatment we observed 21 partial remissions and 3 complete remissions, amounting to a total response rate of 45%. The median duration of response was 39 weeks, and median survival was 56 weeks. Dose-limiting side effects were leukopenia (40 cases) and thrombocytopenia (11 patients). Nausea and vomiting was experienced by 93% of subjects; in 56% of cases it reached WHO stage II-III. Alopecia occurred in 18% of our patients. Our results suggest that PMF represents an active regimen in the treatment of advanced breast cancer and yields a response rate of 45%. Considering that the majority of our patients had not received prior chemotherapy, the question remains open as to whether a 45% response rate outweighs the observed toxicity.