Recombinant granulocyte colony-stimulating factor (G-CSF) [filgrastim and lenograstim] and pegylated G-CSF (pegfilgrastim) have been shown to reduce the severity and duration of chemotherapy-associated febrile neutropenia (FN) when administered prophylactically to cancer patients receiving chemotherapeutic regimens. The American Society of Clinical Oncology (ASCO) evidence-based clinical guidelines published in 1994, 1996 and 1997 recommended primary prophylaxis with G-CSF for cancer patients. The 2000 ASCO update, with the same recommendation, highlights the importance of economic considerations in decision making for CSFs. This paper reviews the available cost-effectiveness evidence on the use of G-CSF as primary prophylaxis against FN in patients with small cell lung cancer (SCLC).Cost-effectiveness ratios from a healthcare payer perspective supported the use of filgrastim as primary prophylaxis for people with SCLC, on the basis of both clinical and economic benefits, treated with chemotherapeutic regimens that have an FN rate in the range of 40-60%. However, when indirect and patient out-of-pocket costs attributable to severe FN are included, available evidence suggests that the risk threshold may be reduced by more than half. Given that FN rates associated with chemotherapeutic regimens for SCLC are generally <40%, then few circumstances would warrant the use of G-CSFs (filgrastim and lenograstim) under the current rule. However, inclusion of indirect costs would lower the cost-effectiveness threshold. Future cost-effectiveness studies of medications such as pegfilgrastim should attempt to capture the societal perspective by incorporating productivity-related costs and using base-case rates of FN reported in the literature.