Hematopoietic growth factors (HGFs) and their receptors play essential roles in regulating hematopoiesis. While several HGFs and cytokines have been identified and characterized, three HGFs have had marked impacts on clinical medicine. We will discuss the clinical uses and unique side-effect profiles of erythropoietin, granulocyte colony-stimulating factor, and thrombopoietin mimetics along with current clinical implications of granulocyte-macrophage colony-stimulating factor and Interleukin-1 in this comprehensive chapter.