To examine the effects of Polygonum multiflorum on white rats with deteriorated immunity caused by methotrexate, first of all, methotrexate was fed to the rats once a day for 4 days. After the immune response of the rats are dereriorated, dried extracts of Polygonum multiflorum mixed in water was fed to the white rats once a day for 144days. The next conclusion was made by examining the rates of B-cells and T-cells of the peripheral blood and the changes in rates of CD4+ T-cells and CD8+ T-cell of the blood sampled from the spleen and peripheral region . Polygonum multiflorum has an effect of increasing immune responses on white rats with deteriorated immunity caused by MTX. Especially the count of CD4+ T-cells of the peripheral blood and the count of CD4+ T-cell of the spleen proved the significant effect o( increasing immune responses statistically . Verification of the effects of the Polygonum multiflorum should be made through comparitive .studies using various immune response indexes. Also additional studies for a modern and practicible application of Polygonum multiflorum seems to be needed.