Abstract We investigated the effects of IL-3, IL-6 and IL-4, alone and in combination with G-CSF and GM-CSF on hematopoietic reconstitution following murine allogenic bone marrow transplantation. The most effective combination for increasing the circulating absolute neutrophil count (ANC) above the control value at day 6 posttransplant was the combination of IL-3 and GM-CSF and showed a significant synergistic effect. When used alone, both IL-6 and G-CSF raised platelet count at day 6 after transplantation (312?10~(9)/L, P=0.02 and 309?10~(9)/L, P=0.01 respectively) compared to control mice(216?109/L). In combination, only IL-3 with G-CSF significantly increased the day 6 platelet count (328?10~(9)/L). We found that neutrophil recovery at day 7 after transplantation was significantly suppressed by IL-4 in a dose-dependent fashion and that the recovery of nentrophils accelerated by IL-3, and G-CSF was also significantly suppressed by IL-4.