The delivery of high-dose epirubicin in patients with advanced breast cancer usually entails serious myelotoxicity and frequent treatment delays. Concurrent administration of G-CSF probably allows the administration of epirubicin on schedule with minimal morbidity. From August 1990 to February 1992, 42 women with advanced breast cancer were treated with six cycles of epirubicin 110 mg/m2 every 4 weeks. Filgrastim 5 micrograms/kg per day for 14 days was administered subcutaneously starting 24 hours after chemotherapy. All patients had multiple metastatic sites, and 39 had visceral metastases. All cases were evaluable for response, toxicity, and survival. Treatment was delayed in only two cases. The actually administered average dose per unit time per patient amounted to 99.6% of the dose prescribed by the protocol. Two (4.5%; 95% confidence interval [C.I.] 0-16%) patients demonstrated a complete response and 14 (33%; 95% C.I. 19-49%) a partial response. Median time to progression was 31 weeks and median survival was 60 weeks. Severe granulocytopenia was seen in six patients; stomatitis and diarrhea in one patient each. Myoskeletal pain was noticed in 23 (55%) patients, while cardiac problems were reported in 3 cases. The present study shows that the prophylactic use of r-met-hu G-CSF allows the administration of high-dose epirubicin every 4 weeks with minimal morbidity and an improved quality of life.