Psoriasis arthropathy (PsA) is a chronic inflammatory arthropathy characterized by the association of arthritis with psoriasis. In this study, clinical, laboratory and radiographic signs of 21 patients (12 males and 9 females), mean age of 42.2 years old, with PsA were assessed. The clinical forms defined by Moll and Wright revealed that oligoarticular pattern was most commonly observed in ten patients (47.6%), followed by polyarticular (5 patients), distal (3 patients), spondyloarthropathy (2 patients), and mutilans (1 patient). Positive rheumatoid factor was detected in three patients and antinuclear antibodies in eight patients, suggesting the involvement of immunological disregulation in this disorder. Twelve patients were onychopathic, of whom 11 showed distal interphalangeal (DIP) joint arthritis. Based on radiologic observation, spur formation of the calcaneus (1 patient) and destructive changes of the articulatio coxa (1 patient) were seen, in addition to the findings such as joint space narrowing, erosive changes, resorptive changes and 'pencil-in-cup' appearances. Non-steroidal anti-inflammatory drugs (NSAIDs) were used in all cases for the control of joint pain, solely or in combination with immunomodulatory drugs such as bucillamine, sulfasalazine, methotrexate, cyclosporin, etretinate, and mizoribine. However, some of those drugs were often ineffective for the joint pain, while effective for cutaneous psoriasis. Immunohistological studies of the biopsied synovial tissues from two patients showed increased expressions of CD45RO and HLA-DR, suggesting that the vast majority of inflammatory cells are mature and activated T-cells. Parallel immunostaining using the involved psoriatic skin from one of the patients also showed enhanced expression of CD45RO, but less expression of HLA-DR as compared with its expression in the synovium. On the other hand, cutaneous leukocyte antigen (CLA) was abundantly detected in the inflammatory cells in the lesional skin, although less expressed in the synovium. These results are consistent with earlier observations suggesting a different subpopulation of inflammatory cells in the skin than the joint.