PURPOSE: To evaluate the clinical activity of a sequential treatment with Adriamycin followed by CMF (cyclophosphamide, methotrexate, fluorouracil) and the relative therapeutic contribution of the two drug regimens given at full conventional doses in metastatic breast cancer. PATIENTS AND METHODS: From August 1990 to February 1993, 44 patients with advanced breast cancer previously untreated with chemotherapy entered the study. Treatment consisted of the intravenous administration of Adriamycin (75 mg/m² on day 1 every three weeks) for four cycles followed by intravenous CMF (cyclophosphamide, 600 mg/m²; methotrexate, 40 mg/m²; fluorouracil 600 mg/m²) on days 1 and 8 every four weeks for four total courses. RESULTS: In 41 evaluable patients, four cycles of full-dose Adriamycin were able to achieve an overall response rate of 75%, including 17% complete remissions. Four cycles of CMF administered after Adriamycin were able to increase tumor response in 64% of evaluable cases. At the end of the sequential treatment program, 78% of 41 patients achieved an objective remission and in 30% of them a clinical complete response was documented. Main side effects, i.e., leukopenia and gastrointestinal disturbances, were moderate and short-lasting. One patient died because of acute myocardial infarction. CONCLUSION: In untreated metastatic breast cancer patients, the sequential administration of Adriamycin and CMF is highly effective at the expense of a moderate toxicity profile that allows high-dose intensity of both drug regimens. CMF treatment after upfront Adriamycin is able to exert a further therapeutic advantage.