A retrospective study has been carried out on 897 psoriatic patients in order to verify the incidence and radiological patterns of psoriatic arthropathy (PA). Site of involved joints, appearance and degree of involvement were correlated with extent of skin disease and blood test results. Sixty-five patients (7%) showed "clinical" arthritis whereas only 20 cases (2.2%) were radiologically positive; among them, 35% were classified as "severe" forms. Peripheral arthritis was observed in all cases, involving the hand in 85% of patients. The distal interphalangeal joints were the most affected location in the feet (78%) and the proximal interphalangeal joints in the hands (94%). The extant small peripheral joints were involved in decreasing rates proceeding proximally. Bilateral and asymmetric involvement was observed in most of the patients; hypertrophic interphalangeal joints erosion was the typical pattern in 100% of cases, evolving in rheumatoid-like ankylosis in 23% of them. Spondylitis and/or sacroiliitis were associated in 50% of patients. No correlation between degree of arthritis and skin disease was found in our series, with the exception of proximal and axial joints arthritis, in which extensive skin disease and severe small joints involvement were associated in 80% of cases. Clear differential features were demonstrated between peripheral PA and rheumatoid arthritis, and between spinal involvement in PA and ankylosing spondylitis. Poor correlation of distal arthritis to psoriatic nail involvement was also demonstrated.