HLA antigens were determined in 25 Finnish patients with both Reiter's disease and skin lesions identical with psoriasis vulgaris. HLA B27 was found in 23 cases (92%) B13 was found in one case, Bw17 and Bw37 were not found at all. The absence of these three "psoriatic" HLA antigens in the present series indicates that the psoriasis-like skin lesions belong to the varying clinical picture of Reiter's disease and not to the HLA linked psoriasis vulgaris.