We assessed the incidence of febrile neutropenia(FN), infection, and relative dose intensity(RDI)with or without the use of pegfilgrastim in breast cancer patients receiving adjuvant or neoadjuvant chemotherapy. Twenty-five patients received 4 cycles of FEC(5-FU 500mg/m2 plus epirubicin 100 mg/m2 plus cyclophosphamide 100 mg/m2 q3w)followed by 4 cycles of docetaxel(75mg/m2 q3w). Ten patients were administered pegfilgrastim as primary prophylaxis throughout all cycles of chemotherapy, and 15 patients were not. The rate of FN was only 7% in patients not undergoing pegfilgrastim therapy. The infection rate and RDI were not significantly different between the 2 groups, but the incidence of fever was lower in patients treated with pegfilgrastim. In patients with early stage breast cancer, the use of primary pegfilgrastim during all chemotherapy cycles should be considered a safe option.