Granulocyte colony stimulating factors (G-CSF) are largely used in the treatment of hematologic disorders to improve both the myelosuppression which might directly result from the disease or indirectly induced by the numerous chemotherapy regimen. G-CSF reduces the depth and duration of neutropenia in lymphoma patients and thus allows the design of more dose intense chemotherapy regimen which were shown to improve outcome particularly in patients with diffuse large B-cell and Hodgkin's lymphoma. G-CSF has been studied in patients with acute leukemias (ALL and AML) both concomitantly to induction chemotherapy to sensitize leukemic cells and after chemotherapy to reduce the duration of neutropenia and incidence of severe infection but it's benefit in these settings is still controversial. Myelodysplastic syndromes (MDS) can benefit from G-CSF in association with erythropoietin, particularly for patients with relative good prognosis according to the IPSS score at diagnosis. Still, an improvement of Quality of life needs to be demonstrated in the vue of the cost of these strategies. In aplastic anemia (AA), G-CSF has been used as a support during infection or in association with immunosuppressive treatments but caution is needed regarding the risk of clonal evolution in AA. The benefit of low dose G-CSF in chronic severe neutropenia is well established but the long term consequences of continuous G-CSF support are not known. Finally, G-CSF given alone or after chemotherapy as become one of the key components of hematopoietic stem cell mobilization allowing the use of high dose therapies with autologous or allogeneic stem cell support.