The family of colony stimulating factors and interleukins influence all aspects of hematopoietic cell proliferation and differentiation. In most instances these hematopoietic growth factors have overlapping, pleiotropic effects and frequently regulate early progenitor cell proliferation and mature cell function. Currently, seven of these factors are in clinical trial: erythropoietin for treatment of anephric anemia, IL-2 in conjunction with LAC therapy, and IL-1, IL-3, G-CSF, GM-CSF, and M-CSF for stimulation of myelopoiesis and granulocyte-macrophage function after chemotherapy, irradiation, or bone marrow transplantation in patients with cancer. G-CSF and GM-CSF have also proved effective in treatment of congenital and idiopathic neutropenias and have had some efficacy in treatment of myeloid leukemias, myelodysplastic disorders, aplastic anemia, and acquired immunodeficiency syndrome (AIDS).