Modern molecular haematology is characterized by the great strides made in the use of cytokines, especially haematopoietic growth factors. These factors constitute a heterogeneous group of molecules that ensure the survival, proliferation and differentiation of the haematopoietic cells. Present detailed knowledge of the structure of the main haematopoietic growth factors and their receptors, and of the cloning and sequencing of their genes, permits the use of genetic engineering to produce recombinant human growth factors whose therapeutic applications have raised very great hopes for clinical haematology. Data obtained from several clinical studies have allowed the use of some of these molecules in France. This is the case concerning erythropoietin (Eprex, Recormon), G-CSF (Neupogen, Granocyte) and GM-CSF (Leucomax), each with specific uses. Others haematopoietic growth factors, such as stem cell factor (SCF) are presently evaluated for their clinical interest. Finally, interleukin 3 (IL3), whose in vitro activities seemed to be of potential interest, has been evaluated during clinical studies. Its toxicity and lack of specificity have been evidenced and do not allow its present utilization. The first part of this review is focused on the general structure and biological activity of haematopoietic growth factors and presents the actual therapeutic field of the use of erythropoietin and the promising application of recombinant thrombopoietin.