Among haematopoietic growth factors, the granulocyte macrophage colony stimulating factor (GM-CSF), the granulocyte colony stimulating factor (G-CSF) and, more recently, interleukin-3 have been used in therapeutics mainly to try to reduce the duration of aplasia after chemotherapy followed or not by bone marrow transplantation in solid tumours and in leukaemias. In addition, interleukin-3 reduces the need for red cell and platelet transfusions. A concomitant reduction of death from infection, antibiotic use and duration of stay in hospital has been demonstrated by some randomized studies, but data are lacking to evaluate its practical and economic value. In acute myeloid leukaemia haematopoietic growth factors sensitize leukaemic cells to chemotherapy in vitro, but the clinical usefulness of this finding remains to be assessed. The stimulating and differentiating actions of haematopoietic growth factors on the bone marrow in vitro seems to have a clinical value in myelodysplastic syndromes where randomized studies have shown a rise in the number of cells after administration of these factors. However, whether long-term treatment will prolong the survival of patients with myeloplastic syndromes remains to be demonstrated.