This phase II trial studied the efficacy and toxicity of docetaxel-epirubicin, supported by granulocyte colony-stimulating factor, as first-line chemotherapy in metastatic breast cancer. Patients received epirubicin (60 mg/m2) followed 1 hour later by docetaxel (80 mg/m2) every 3 weeks for a maximum of 8 cycles or until disease progression. Prophylactic granulocyte colony-stimulating factor (5 micrograms/kg) was administered daily for 5 days. Sixty-nine patients were evaluable for efficacy and toxicity. Objective responses occurred in 45 patients (65%; 95% confidence interval: 53-76%), with 11 (16%) complete responses and 34 (49%) partial responses. Responses were observed at all metastatic sites. The median response duration was 8 months (range 4-68), median time to progression was 10 months (range 4-68) and median overall survival was 24 months (range 7-68): neutropenia was dose limiting (46% grade 3-4 toxicity). The left ventricular ejection, fraction measured in 50 patients, fell below normal in 14 patients (28%), 8 patients had grade 1 and 6 grade 2 cardiotoxicity, but none developed congestive cardiac failure. The docetaxel-epirubicin regimen is extremely effective in poor prognosis breast cancer patients with visceral metastases, with significant overall and complete responses, followed by prolonged survival in responders. Although myelosuppression remains the major toxicity, prophylactic GCSF administration was associated with a small percentage of neutropenic fever.