Epirubicin and paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is an active combination for the treatment of metastatic breast cancer. A multicenter pilot phase II trial evaluated this combination in 35 patients treated with epirubicin 75 mg/m2 given as a 1-hour infusion, immediately followed by paclitaxel 200 mg/m2 given as a 3-hour infusion every 3 weeks. All patients had metastatic disease and had received a maximum of one chemotherapy regimen for advanced disease. A 43% response rate was observed in 30 evaluable patients, with two complete responses (7%) and 11 partial responses (37%). All patients were evaluable for toxicity. Hematologic toxicity was common and dose limiting. All patients underwent blood counts three times weekly. Grade 4 neutropenia was extremely common (91%), occurring at approximately days 10 to 12 and resolving rapidly in most cases. Thrombocytopenia was rare. Dose reductions were necessary in 10 patients, primarily for myelosuppression, but due to neuropathy in two patients. Alopecia was universal. Cardiac function was measured in all patients every two cycles. Among the first 24 evaluable patients, left ventricular ejection fraction decreased to below 40% in three patients, all of whom had received prior anthracyclines. Treatment was discontinued in one patient, who experienced no further deterioration. Under the auspices of the United Kingdom Coordinating Committee for Cancer Research, a randomized phase III study has been initiated in the United Kingdom to compare this combination of epirubicin/paclitaxel with combination epirubicin/cyclophosphamide. The primary end point of this study is progression-free survival, and the intention is to recruit 350 to 700 patients over the next 2 years.