Abstract: One hundred and five cases of psoriasis were treated by PUVA therapy,The cell mediated immunity and humoral immunity were examined in each case. The results showed that their LTT values and sesum IgM, IgG values were significantly changed as compared with the normal control group(P<0.01),the former two values decresed, but the latter increased, Five immunological tests were per formed on 31 cases before and after PUYA therapy, that result showed.that after PUVA therapy the serum IgM value increased and LTT value decreased significantly(P<0.01).These showed that the immun-ological function of these patients were changed,especially cell mediated immunity might be supgressed. This might increase the risk of carcinogenesis, shortened the duration of remission, and increased the severity of the disease when relapse occurred.