Anthracyclines and taxanes are very effective drugs in the treatment of advanced breast cancer. With G-CSF support, the dose-intensity of this combination can be increased by reducing the interval between chemotherapy cycles, the so-called 'shortening of cycle time'. We treated 36 patients with advanced breast cancer in a multicentre phase I/II study. The treatment regimen consisted of epirubicin 75 mg m(-2) followed by paclitaxel 135 mg m(-2) (3 h) in combination with G-CSF. At least six patients were treated in each cohort and were evaluated over the first three cycles. Starting at an interval of 14 days, in subsequent cohorts of patients the interval could be shortened to 10 days. An 8-day interval was not feasible due mainly to incomplete neutrophil recovery at the day of the next scheduled cycle. In the 10-day interval cohort it was feasible to increase the paclitaxel dose to 175 mg m(-2). The haematological and non-haematological toxicity was relatively mild. No cumulative myelosuppression was observed over at least three consecutive cycles. In combination with G-CSF, epirubicin 75 mg m(-2) and paclitaxel 175 mg m(-2) could be safely administered every 10 days over at least three cycles, enabling a dose intensity of 52 and 122 mg m(-2) per week, respectively.