The importance of dose-intensity has been suggested in breast cancer. The aim of this study was to evaluate the feasibility of a high-dose intensity doxorubicin-cyclophosphamide regimen with supporting G-CSF and blood stem cells. Twenty-five patients with non-metastatic breast cancer received four cycles of doxorubicin (75 mg/m2) and cyclophosphamide (3000 mg/m2) at 3 week intervals. Apheresis was performed after the first cycle and if necessary after the second cycle. Stem cells were reinfused after the third and fourth cycles. G-CSF was started on day 3 of each cycle (5 microg/kg/day) and was stopped the day before the last apheresis or when absolute neutrophil count was above 0.5 x 10(9)/l. Median received dose-intensity was respectively 25 mg/m2/week (range 22-26) and 1000 mg/m2/week (range 904-1065) for doxorubicin and cyclophosphamide. Grade IV thrombocytopenia occurred in 8% of cycles. Two patients needed platelets and 12 red cell transfusion. Fifteen patients were readmitted for a median duration of 4 days (range 1-7). We have established a safe, outpatient, high-dose intensity doxorubicin-cyclophosphamide regimen with supporting G-CSF and blood stem cells which can be submitted for comparison with the current standards.