Objectives: The purpose of this study was to verify the effect of Palmiboshinwhan (PMBSW) in methotrexate (MTX)-induced immunosuppressed SD rats. Methods: The test articles were once a day dosed for 14 days by gastric gavage from 2 days after last MTX-dosing, and changes in body weight, spleen weight and total blood leukocyte numbers were observed with total lymphocyte numbers, B and T lymphocyte percentages, CD3+CD4+, CD3+/CD8+, CD4+/CD8+ T lymphocyte percentages in the blood and spleen, the serum interleukin (IL)-2 levels and the productivity of IL-2 of splenic cells. Result & Conclusion: It is concluded that PMBSW has relatively good immunostimulating effect in the MTX-induced immunosuppressed SD rats. Theefficient dosage was considered above 500mg/kg. In addition, it is considered that the immunostimulating effect of PMBSW was mediated to both the B and T lymphocytes. The more favorable effects were detected in T lymphocytes rather than B lymphocytes, and PMBSW showedrelatively good stimulating potential against CD4+ T lymphocytes but not any stimulating effect against CD8+ T lymphocytes in the present study.