Abstract: Serum and urine alkaline ribonuclease activity detected in 101 patients with psoriasis in different stages of illness is reported in this article. The results showed that the alkaline ribonuclease activity unit(RALT) in patients with psoriasis were markedly higher than that of normal control group(P<0.001),with RAU in progressive stzge > RAU in stationary stage}RAU in resolving stage (P<0.05-0.001).The authors consider tliat the change of serum and urine RNase activity in parallel with the stage of skin lesions might have a cerlain value in explaining the pathogenesis,selecting the therapeutic method,and judging the prognosis of psoriasis.