Objective : To investigate the effect of Samilshinkihwan(SISKW) on white rats with deteriorated immunity caused by methotrexate. Methods : The test articles were dosed once a day for 14 days by gastric gavage at a dosage 1000, 500 and 250mg/kg/10ml of SISKW from 2 days after last MTX-dosing, and changes in body weight, spleen weight, total blood leukocyte numbers, total lymphocyte numbers, B and T lymphocyte ratio, CD3+CD4+, CD3+/CD8+ and CD4+/CD8+ T lymphocyte ratio in the blood and spleen were measured. In addition, the serum interleukin (IL)-2 levels and the productivity of IL-2 of splenic cells were also demonstrated in this study. Results : The changes on body weight increased significantly in the 1000mg/kgof SISKW group. The changes on the spleen weight, the total blood leukocytenumbers, the total lymphocyte numbers in the blood and spleen, the ratio of T-cell in the blood and spleen and the ratio of CD3+CD4+ T-cell in spleen increased significantly in all SISKW groups as compared with the control group. The ratio of CD4+/CD8+ T-cells in blood increased significantly. The serum IL-2 levels and productivity of IL-2 of splenic cells increased significantly in 1000 and 500mg/kg SISKW groups as compared with the control group. Conclusions : Samilshinkihwanhas an effect of increasing immune responses, especially on cellular immune responses, in white rats with deteriorated immunity caused by methotrexate.