Recently biotechnologic progress has, through the technique of the recombinant DNA, allowed a low cost production of large amount of several growth factors. Such a large availability has made possible to either carry out deeper investigations on the physiopathology of the hemopoietic regulation and perform new therapeutic approaches under different pathologic conditions. The most interesting acquisition concerning the biology of hemopoiesis to which such investigations have addressed us is the inadequacy of the protocols adopted till now. Such protocols considered only a simple vision of an elective action of a given growth factor during an exact maturation period of a determined cell colony. On the contrary, it was possible to point out a close network of inter-relationship among the different factors, which sometime impedes a clear distinction for each single factor, between actions of competence and progression in the cell maturation phenomena. However, the present uncertainty pertaining to the regulation of hemopoiesis has not impede the performance of clinical trials with positive findings in several pathologic conditions. The administration of recombinant erythropoietin has for example allowed to intervene in a resolutive way on the anemia in uremic subjects, and seems giving satisfactory results also in subjects with non renal origin anemic conditions. Satisfactory results were also obtained through the use of the Granulocyte-Macrophage CSF and of the Granulocyte-CSF, which by preventing neutropenia have allowed the performance of more adequate chemotherapeutic protocols in neoplastic subjects. New interesting perspectives are now coming for the use of Interleukin-3 in the treatment of the aplastic anaemia.