(1) Cancer chemotherapy often causes haematological complications, in particular neutropenia, which can have grave consequences in terms of the risk of infections (increasing with the degree and duration of neutropenia) and the need for modifications in chemotherapy protocols (longer intervals between cycles or dose reductions). (2) In France, three haematopoietic growth factors are licensed to stimulate leukocyte production: filgrastim (unglycosylated granulocyte colony-stimulating factor (G-CSF)), pegfilgrastim (pegylated filgrastim), and lenograstim (glycosylated G-CSF). (3) The main adverse effects of these three growth factors are joint and bone pain, a flu-like syndrome, and reactions at the injection site. (4) G-CSF has provided disappointing results in primary prevention, and its use is only justified for patients receiving chemotherapy that causes febrile neutropenia in at least 40% of cases: patients with acute leukaemia, elderly patients, and patients with cancer-related neutropenia or poor general status, etc. In these patients, G-CSF reduces the incidence of febrile neutropenia and, possibly, the risk of hospitalisation. A meta-analysis of 11 comparative trials involving about 1500 patients with non Hodgkin's lymphoma showed only a reduction in the incidence of febrile neutropenia and infections. (5) In the prevention of recurrences of neutropenia on continuing chemotherapy, only one trial, involving patients aged over 60 with high-grade non Hodgkin's lymphoma, showed an improvement in survival time with filgrastim (survival rate: 64.3% with filgrastim versus 49% with placebo, after a median follow-up of 40 months). Until these results are confirmed in other clinical trials, reduction in the intensity of chemotherapy (dosage, frequency) is generally recommended. (6) Curative treatment of neutropenia with G-CSF is only warranted for febrile patients with a high risk of severe infections requiring lengthy hospitalisation. Two meta-analyses, one including 8 trials and the other including 13 trials, involving a total of about 1500 patients, only showed a reduction in the length of hospitalisation.