Among 77 patients hospitalized with psoriasis, 30 (39%) had psoriatic arthritis. Arthiritis was more frequent (P less than 0.05) in those with extensive psoriasis (grades 3 and 4) than in those with less extensive psoriasis (grade 1 and 2). Temporally, flares in skin and joint disease were not closely related. The Moll-Wright classification of psoriatic arthritis into five clinical groups could be loosely applied to our patients. However, sacroiliitis (present in 33% of the patients) was seen in all five groups and was related to HLA-B27 antigen. Although there was no positive correlation between extent of psoriasis and serum urate level, four patients had gout. Mean serum urate level was higher (P less than 0.05) in females with psoriatic arthritis than in females with psoriasis alone. Antinuclear antibodies were found in 6 of 19 patients with psoriatic arthritis and in none of the 11 patients with psoriasis alone.