In a pre-clinical primate model, the effect of a single intravenous injection of rh-GM-CSF (50 micrograms/kg), rh-IL3 (20 micrograms/kg), rh-IL-1 beta (1 micrograms/kg), rh-G-CSF (50 micrograms/kg) and rh-pIXY 321 (50 micrograms/kg) on peripheral blood mononuclear cell and hematopoietic stem cell concentration was determined. The results indicated that administration of a single dose of rh-IL-1 beta increased the concentrations of hematopoietic stem cells, including CFU-GM progenitors and precursors to CFU-GM. No toxicity was noted with this procedure. None of the remaining cytokines tested caused a significant increase in the peripheral blood hematopoietic stem cell concentration when administered in this manner and only G-CSF caused an increase in peripheral blood mononuclear cell concentrations. Autologous transplantation with limiting numbers of peripheral blood mononuclear cells (1 x 10(7) cells/kg) collected either 24 or 72 h following injection of 1 microgram/kg rh-IL-1 beta conferred a survival advantage to recipients compared with controls. These results imply that a single intravenous administration of rh-IL-1 beta may increase the concentration of peripheral blood stem cells to levels sufficient for transplantation.