Filgrastim (granulocyte colony-stimulating factor), which is administered by daily subcutaneous injection after cytotoxic chemotherapy, shortens the duration of chemotherapy-induced neutropenia and lowers the risk of infection. In children treated with dose-intensive chemotherapy, filgrastim reduces the duration of severe neutropenia and, as a result, has become a standard component of the treatment regimen. Filgrastim-SD/01 (AMGEN), which is produced by PEGylation of the amino-terminus of filgrastim, is a sustained duration form of granulocyte colony-stimulating factor. In phase I and phase II trials in adults, a single dose of Filgrastim-SD/01 appears to be equivalent to daily dosing of filgrastim in enhancing neutrophil recovery and has a comparable adverse event profile.