Hematopoietic growth factors (HGF) are glycoproteins controlling proliferation, differentiation and function of bone marrow derived cells. Results of recent studies, both in vitro and in vivo, in animal models, indicate that these molecules might have a therapeutical value in several different clinical settings. Thanks to advances in the expression of recombinant genes. HGF have recently become available in sufficient quantities to be tested in clinical investigation. During the last few years, a number of phase I/II trials have been performed with the use of recombinant colony stimulating factors and erythropoietin, suggesting the efficacy of these substances in treating diseases associated with hematopoietic failure or impaired cell function. This review article takes a critical look at the most important recent preclinical and clinical experience on HGF, and also examines some of the future directions in which clinical medicine will probably benefit from these molecules.