Myelosuppression is the major dose-limiting toxicity of chemotherapy in small cell lung cancer (SCLC). The capacity of colony stimulating factors (CSFs) to stimulate granular neutrophil recovery may be of great value to prevent or cure febrile neutropenia and to increase dose-intensity. The aim of this review was to assess the current use of CSFs in SCLC on the basis of experimental and clinical data. Primary CSF administration has been shown to reduce the incidence of febrile neutropenia, hospital admission rate, and antibiotic use subsequent to cyclophosphamidedoxorubicin-high dose etoposide (CDE) chemotherapy, without improvement of survival or disease control. Primary CSF administration may be recommended when the expected incidence of febrile neutropenia is at least 40%. This benefit has not been established with less myelosuppressive regimens, such as cisplatin-etoposide (PE), which remains an alternative combination of SCLC when standard doses are used. A trial comparing high-dose CDE + CSF with PE would be of considerable interest. There is currently little clinical basis for the use of CSFs to increase chemotherapy dose-intensity, outside clinical trials. Peripheral blood progenitor cells mobilized with CSFs offer interesting prospects. Further studies, with later initiation, shorter duration or lower doses of CSFs, are warranted to improve the cost-effectiveness of CSFs. CSF therapy in addition to antibiotics is normally not justified in febrile neutropenia, except perhaps in selected patients with sepsis syndromes, hypotension or pneumonia.