Febrile neutropenia (FN) is a severe consequence of myelosuppressive therapy. The European Organisation for Research and Treatment of Cancer recently published guidelines on the use of granulocyte colony-stimulating factor (G-CSF) to prevent FN in patients with malignant disease. In this review, the impact of these guidelines on breast cancer treatment is discussed. A brief summary of FN in breast cancer is given, and patient-related and treatment schedule-related risk factors for FN are reviewed for the adjuvant/neoadjuvant and metastatic disease settings. Primary G-CSF support is recommended if the overall FN risk is > or = 20%, or if a reduction in dose-intensity is associated with a poorer outcome. Any formulation of G-CSF is recommended. The utility of G-CSF in reducing the incidence of FN and enabling treatment regimens is discussed.