As of August 1984, 115 women with advanced breast cancer have been randomized to receive a combination of either cyclophosphamide, Novantrone (mitoxantrone) and 5-fluorouracil (CNF) or cyclophosphamide, Adriamycin (doxorubicin) and 5-fluorouracil (CAF). Seventy-one percent of all patients were post-menopausal and 44% of CNF patients and 57% of CAF patients were estrogen receptor (ER) negative. Slightly over 30% of all patients had received hormonal therapy or chemotherapy in an adjuvant setting. Hematologic toxicity was similar in regard to platelet counts but slightly lower nadirs were experienced with CNF therapy than with CAF. However, there were fewer dosage decreases with CNF. Significantly less nausea and vomiting were observed with the CNF regimen compared to CAF. Moreover, alopecia was reduced appreciably in patients who received CNF. The response rate to CNF for the first 38 eligible and evaluable patients was 42%, and for 53 eligible and evaluable patients who received CAF the response rate was 45%, a non-significant difference. Median response durations were similar also, 140 days for CNF and 168 days for the CAF regimen. Time to treatment failure was similar for both regimens. CNF is an effective regimen for patients with advanced breast cancer, with less toxicity than CAF.