Chemotherapy-induced neutropenia (CIN), the most common dose-limiting toxicity of cancer chemotherapy, is associated with numerous clinical, personal, and economic consequences. The principal strategies for managing CIN are reducing the dose intensity of the chemotherapy, using antibiotics, and using colony-stimulating factors (CSFs). Reducing or delaying the chemotherapy dose is effective, but this can compromise treatment outcomes. Antibiotics can be lifesaving, but they are associated with numerous adverse effects and the emergence of resistant pathogens. The granulocyte CSF (G-CSF) filgrastim can reduce the incidence, duration, and severity of CIN, as well as the risk of infection, in patients treated with myelosuppressive chemotherapy. The availability of pegfilgrastim, a sustained-duration G-CSF that has benefits comparable to those of filgrastim with a single injection per chemotherapy cycle, has simplified CSF therapy.