The changes of the immune function of rheumatoid arthritis before and after the Tibetan medicated-bath was observed. It showed a higher level of the rheumatoid factor (RF) titre, immunoglobulin (Ig) G, M, A and CD4 cells, but the CD8 cells was obviously lower before the treatment. Clinical data indicated that the medicated-bath had significant effective rate. In order to elucidate the mechanism of the medicated-bath upon rheumatoid arthritis the RF titre, Ig level, complement C3, 3H-TdR incorporated with lymphocytes transformation and CD3, CD4, CD8 cell level were assayed. Results showed that RF titre decreased after the bath and the negative transforming rate reached 70.6%, Ig level obviously dropped as well as the number of CD4 cells while CD8 cell level increased. The transforming stimulation index of lymphocyte cells obviously decreased. All of the above mentioned showed that there was a higher concentration of the enhancing factor of interleukin-2 (IL2-EF) involved in lymphocyte culture of rheumatoid arthritis patients. They suggested that the Tibetan medicated-bath had an immunomodulating effect on rheumatoid arthritis patients through increasing the level of CD8 cells and reducing CD4 cells.