Abstract: The circulating immune complex and mixed rosette formation test etc. of 109 in-patients with psoriasis vulgaris were examined. Psoriasis might be an(cutaneous)immune complex disease was suggested.The results of Cab sensitized yeast agglutination test in 39 cases and red cell immune test in 19 cases showed that the level of circulating immune complex of patients with psoriasis might increase. Assays of immunoglobulins demonstrated the increased values of IgG and IgA and the decreased level of C₃ also might support that psoriasis was related to immune complex. The results of E. Y, mixed rosette formation test in 55 cases showed that B cell decreased, and N cell and D cell increased. PHA lymphocyte transformation rate also decreased prominently. It is thought that the function of cell mediated immunity of psoriasis might be low, and the function of humoral immunity of psoriasis also might be deficient.