In 100 consecutive patients admitted to the hospital for control of severe psoriasis, 25 had radiologic changes characteristic of psoriatic arthritis. Twenty had erosions and mild sclerosis around the sacroiliac joint; in eight of these, asymptomatic sacroiliac changes were the sole manifestation of musculoskeletal disease. Twelve had vertebral syndesmophytes, 11 had terminal interphalangeal joint changes, and 10 had peripheral joint involvement.