Protective effect of agent WR-2721 on hematopoiesis and prophylaxis for the combined radiation-burn injury were investigated in the present study. It was found that pretreatment with WR-2721 could significantly raised the survival rate and suwival time of mice with the combined radiation-burn injury. Prophylactic use of WR-2721 resulted in an increase of LD50 value from 5.19 Gy of the control to 9.53 Gy of the pretreatment. DRF (dose reduction factor) was 1.84. Prophylactic effect of WR-2721 was gained by the immediate use before irradiation with the dose of 200 mg/kg. Pretreatment of WR-2721 in mice with the combined injury brought about a lesser decrease in peripheral WBC count and an earlier recovery compared with the control. Bone marrow myelocyte and monocyte counts were markedly higher than the control at day 1 and 7 postinjury and bone marrow hematopoietic stem cell count was significantly higher than the control at day 7 and 14. Prophylactic effect of WR-2721 on the combined radiation-burn injury was at least partially due to its protective effect on hematopoiesis.