Abstract: To investigate the cellular immunity abnormalities in patients with ankylosing spondylitis（AS）, peripheral blood lymphocyte subpopulations, NK cell activity and the production of IL-2 were analysed and compared with those of healthy controls. The results showed that the percentage of T4, T8, Tac and the ratio of T4/T8 in patients with AS were comparable to healthy controls. Marked decrease of NK cell activity and poor response to IL-2 stimulation were also noticed. The data also showed that there was significant overproduction of IL-2 in patients with AS. We concluded that there were severe cellular immunity abnormalities in patients with AS which may contribute to the pathogenesis of the disease.