A multicenter phase III randomized study compared the efficacies of two adjuvant polychemotherapeutic regimens in 145 patients with stage II node-positive breast cancer. The standard chemotherapy combination, CMF (cyclophosphamide, methotrexate, 5-fluorouracil), was administered to 77 women. The experimental protocol, CNF (cyclophosphamide, mitoxantrone, 5-FU), in which mitoxantrone (Novantrone) replaced methotrexate, was given to 68 patients. Follow-up of the 145 patients by six participating hospitals showed no statistically significant difference (p = 0.6) between the two treatment regimens during a median follow-up of 4.5 years in terms of overall survival. There was, however, a significant advantage (p = 0.04) in the disease-free survival for those receiving mitoxantrone (mean survival 4.4 years for CNF versus 2.7 years for CMF). Toxic side effects associated with CNF (particularly alopecia and myelotoxicity) were relatively more frequent but acceptable and did not lead to dose reduction. In light of its association with improved disease-free survival in this study, larger studies should be undertaken on the role of mitoxantrone as adjuvant treatment in stage II breast cancer.