Amifostine protects normal tissues from the cytotoxicity of chemotherapy and radiotherapy and has an effect a growth factor both in vivo and in vitro. To evaluate its possible hemopoietic promoting activity, the authors studied the effect of WR-2721 on cord blood and bone marrow progenitors from children with hematological disorders and normal controls in semisolid cultures after preincubation with 0.1-1000 microM amifostine. Amifostine enhanced the growth of BFU-E in autoimmune neutropenia but inhibited CFU-GM development. It also exerted an inhibitory effect upon growth of committed progenitors in the groups studied (acute lymphoblastic leukemia, Langerhans cell histiocytosis), including cord blood and marrow of healthy controls.