Granulocyte colony stimulating factor (G-CSF) has proven efficacy in the prophylaxis of chemotherapy induced neutropenia and is associated with a reduction in the duration of neutropenia, febrile neutropenia, hospitalisation and intravenous antibiotic use. It is an effective mobiliser of peripheral blood progenitor cells and is used in many countries to mobilise and provide a source of stem cells for autologous and allogeneic bone marrow transplantation. The longevity of G-CSF action is limited by its short half-life, necessitating daily injections. Pegfilgrastim (Neulasta, Amgen, Inc.) is a novel form of filgrastim (G-CSF) with a sustained duration of action. Single dose pegfilgrastim has been shown to be as safe and effective as daily filgrastim in reducing the incidence of chemotherapy induced neutropenia. Pegfilgrastim provides clinical and quality of life benefits for patients as a result of its once per cycle administration. It is licenced in the US for use in the prophylaxis and treatment of chemotherapy induced neutropenia. Clinical trials to evaluate its ability to mobilise peripheral blood progenitor cells are ongoing.