In order to investigate the effect of Goamshimshinhwan(GASSW) on SD rats with deteriorated immunity caused by methotrexate. Methotrexate was fed to the SD rats once a day for 4 days. After the immune responses of the at a dosage 1,000, 500 and 250mg/kg/10ml. and the changes on body weight and gains, spleen weight, total blood leukocyte numbers, total lymphocyte numbers, the percentage of B-cell, T-cell, CD3+CD+4 T-cell, CD3+CD8+ T-cell and CD4+/CD8+ T-cell ratios in the bolld and spleen were observed. In addition, the serum IL-2 levels and productivity of IL-2 of splenic cells were also demonstrated in this study. The changes on body weight were increased significantly in 100 and 500mg/kg of GASSW groups and the changes on body gain were increased significantly in 1000mg/kg of GASSW groups as compared with control group. The changes on the spleen weight (absolutely or relatively) were increased significantly in all GASSW groups as compared with control group. The total blood leukocyte numbers were increased significantly in 1000 and 500mg/kg of GASSW groups as compared with control group. The total lymphocyte numbers were increased significantly in all GASSW groups in the blood and increased significantly in 1000 and 500mg/kg of GASSW goups in spleen as compared with control group. The percentage of B-cell and T-cell were increased significantly in 1000mg/kg of GASSW groups in the blood and increased significantly in 1000 and 500mg/kg of GASSW groups in spleen as compared with control group. The percentage of CD3+CD4+ T-cell and the serum IL-2 levels and productivity of IL-2 of splenic cells were increased significantly in 100 and 500 mg/kg of GASSW groups in the blood and spleen as compared with control group. The percentage of CD3+CD8+ T-cell were increased significantly in 1000mg/kg of GASSW groups only in spleen as compared with control groups. The CD4+/CD8+ T-cell ratios were increased significantly in 1000 and 500mg/kg of GASSW groups only in the blood as compared with control group. Goamshimshinhwan(GASSW) has immuno-stimulating effect on SD rats with deteriorated immunity caused by methotrexate.