The aim of the study was to define a regular and tolerable dose of the epirubicin-docetaxel combination in first-line chemotherapy of patients with metastatic breast cancer. Sixty-five women with measurable and/or evaluable disease were treated with epirubicin escalated from 60 to 110 mg/m(2) according to 5 dose levels, in combination with a fixed dose of 75 mg/m(2) docetaxel, every 21 days for 6 cycles, without preventive use of hematopoietic growth factors or antibiotics. Forty-three women received adjuvant chemotherapy, consisting of anthracyline- or anthracenedione-based regimens in 39 cases (60%). Twenty-seven women were treated in the phase I study (3 at epirubicin 60 mg/m(2), and 6 at each subsequent dose level). Dose-limiting toxicity consisted of grade III asthenia and febrile neutropenia (epirubicin 75 mg/m(2)), grade IV thrombopenia and grade III asthenia (epirubicin 90 mg/m(2)), grade IV stomatitis and grade III diarrhea (epirubicin 100 mg/m(2)), and grade III diarrhea (epirubicin 110 mg/m(2)). In the phase II study, an additional 38 women were treated at epirubicin 90 mg/m(2) and epirubicin 100 mg/m(2). During the 349 cycles delivered, grade IV neutropenia occurred in 90%; febrile neutropenia requiring hospitalization occurred in 62 (17.8%) and lasted more than 3 days in 12 (3.4%). Nonhematologic toxicity was acceptable. Three left ventricular ejection fraction depressions occurred and normalized during follow-up. The overall response rate in the 62 evaluable women was 69.4% (range: 58--81%), with a median duration of 7.8 months. After 26 months of follow-up, the median time to progression was 9.1 months and median overall survival was 22.7 months. On the basis of efficacy and toxicity, the recommended dose of the combination is epirubicin 100 mg/m(2) plus docetaxel 75 mg/m(2).