Many chemotherapy regimens cause myelosuppression, which can result in febrile neutropenia and potentially lead to serious infections. The risk of neutropenia and its complications can be reduced with filgrastim, a granulocyte-colony-stimulating factor. Filgrastim is safe and effective, but it is cleared rapidly from the body (predominantly through the kidneys) and requires daily administration for up to 14 days. A pegylated form of filgrastim, pegfilgrastim, has been developed by attaching a polyethylene glycol molecule to filgrastim. Pegfilgrastim has an extended circulation half-life and self-regulating, patient-specific pharmacokinetics, making it possible to give the treatment as a single dose once per chemotherapy cycle. Clinical trials have shown that a single, subcutaneous dose of pegfilgrastim is as safe and effective as daily filgrastim injections in patients treated with myelosuppressive chemotherapy. In addition, a single, 6 mg fixed dose of pegfilgrastim per chemotherapy cycle is sufficient in adult patients, regardless of their body weight, making pegfilgrastim a simple, effective, and well-tolerated option for managing chemotherapy-induced neutropenia.