Haematological growth factors constitute a major development in haematological and oncological practice. There are many questions raised as to their place and their optimal usage in the treatment of bronchial cancer. Growth factors enable the dose of chemotherapy to be increased by 20-40%, the limiting factor being thrombocytopenia and non-haematological toxicity. Nevertheless, a dose response relationship has never been clearly shown with chemotherapy for small cell and non-small cell carcinoma. Prescribing growth factor prophylactically enables a reduction in both the depth and duration of neutropaenia. Randomised studies which have evaluated G-CSF and GM-CSF for prophylaxis of infections in patients treated for small cell carcinoma lead to the same conclusions: a diminution in febrile episodes with neutropaenia, the duration of hospital stay and in the prescription of antibiotics. It seems justifiable to prescribe growth factors in patients presenting with a febrile illness and aplasia after the first treatment without growth factor in small cell carcinoma. It seems equally legitimate to prescribe these drugs in non-small cell carcinoma which have responded to chemotherapy at the price of aplasia. Outside these circumstances, it does not seem appropriate to prescribe these factors as first intention to those patients receiving conventional doses of chemotherapy who had not been treated before. There does not yet exist clear data for their use in established febrile conditions. The economic assessment has been limited to studies of minima-listing costs. No study of cost-effectiveness and cost-utility has been carried out to date.