Sixty-four consecutive patients with locally advanced (n = 7) or metastatic breast cancer (n = 57), were treated with a combination of laevofolinic acid 100 mg m-2 plus 5-fluorouracil 340 mg m-2 i.v. on days 1-3, cyclophosphamide 600 mg m-2 i.v. on day 1 and epirubicin 90 mg m-2 i.v. on day 1. Epirubicin dose was progressively escalated by 10 mg m-2 per cycle up to 120 mg m-2 in the absence of dose-limiting toxicities. Granulocyte colony-stimulating factor (G-CSF) was given subcutaneously in order to prevent neutropenia. Epirubicin dosage could be increased to 100 mg m-2 in 53 patients (87%), to 110 mg m-2 in 31 patients (51%) and to 120 mg m-2 in 18 cases (30%). In most patients the dose-limiting toxicity was represented by myelosuppression. A statistically significant correlation was found between median white blood count (WBC) or absolute neutrophil count (ANC) nadir and epirubicin dose level (P = 0.009; P = 0.008). Moreover, a statistically significant correlation was observed between the number of chemotherapeutic cycles, nadir ANC and WBC and the occurrence of anaemia and thrombocytopenia of increasing severity. These data suggest the occurrence of progressive cumulative bone marrow toxicity. Although patients who reached different epirubicin levels showed differences in mean dose intensity, such differences were not statistically significant. No correlation was found between the increase in dose intensity and type, rate or duration of objective responses. In patients with metastatic breast cancer the overall response rate was 72% (95% CL 66-78%) with a 25% complete response rate. Median duration of response was 10 and 13 months respectively for complete and partial responses. All patients with locally advanced breast cancer had an objective response and underwent radical mastectomy. Projected median survival of the whole series of patients with metastatic breast cancer was 20 + months. These data demonstrate that the combination of 5-fluorouracil with laevofolinic acid, cyclophosphamide and epirubicin is very active against metastatic breast cancer. Use of G-CSF allows epirubicin dosage to be increased up to 120 mg m-2 cycle-1, but its use may be linked to the occurrence of sometimes severe cumulative haematological toxicity.