32 consecutive early breast cancer patients were treated to evaluate the feasibility of an accelerated CEF regimen (cyclophosphamide 600 mg/m2, epirubicin 60 mg/m2 and 5-fluorouracil 600 mg/m2) given intravenously every 2 weeks for six cycles together with granulocyte colony stimulating factor, 5 micrograms/kg/day subcutaneously from day 4 to day 11. One hundred and eighty two out of 192 planned cycles (95%) were administered. Toxicity was mild: no cases of grade IV non-haematological toxicity and only one episode of grade IV granulocytopenia were observed. Delays or dose reductions of anti-neoplastic drugs occurred in 14 cycles (7.7%). The mean duration of six cycles of treatment was 71 days (planned 70) and 93% of average planned dose intensity was actually administered. The short course CEF therapy is a feasible, well tolerated outpatient chemotherapy regimen, allowing a 46% increase in dose intensity compared with a standard CEF regimen given every 3 weeks. A randomised study comparing this regimen to a standard CEF regimen is now in progress in early breast cancer patients.