AIM: To examine the efficacy of Saenghyuldan and its components, Ginseng Radix, Paeoniae Radix Alba, andHominis Placenta extracts (SHD, GR, PRA, and HP, respectively) on the hemopoiesis in a myelosuppression modelsystem. METHODS: Susceptibility to cyclophosphamide (CP) and S 180 carcinoma was determined in SHD, GR,PRA, and HP-treated mice. Analysis of peripheral blood and bone marrow cells was demonstrated by changes incell types and histopathologic examination. The expression of cytokine mRNAs involved in hemopoiesis wasexamined by RT-PCR. RESULTS: SHD and its seperated components (GR, HP, and PRA, respectively) signifi-cantly increased the survival in CP- and S180-treated mice. The hematology data demonstrated that all the agentsaugmented monocyte and leucocyte counts in the peripheral blood and increased bone marrow density and the ratioof leukocyte to erythrocyte in the bone marrow. These findings were positively correlated with the up-regulation ofcytokine mRNA expression such as granulocyte colony-stimulating factor (GM-CSF), erythropoietin (EPO),thrombopoietin (TPO), stem cell factor (SCF), and c-Kit. CONCLUSION: SHD is an effective remedy for thebone marrow failure and myelosuppression occurring during chemotherapy.