To determine the presence and clinical significance of antibodies to cyclic citrullinated peptides (anti-CCP) in psoriatic arthritis (PsA).We performed a cross-sectional study on 102 outpatients (56 men) with PsA consecutively recruited from a tertiary referral center. Median disease duration was 36 months (interquartile range 21-81). All patients were investigated for peripheral joint and axial involvement, enthesitis, and dactylitis. Laboratory investigations included anti-CCP, assessed by enzyme-linked immunosorbent assay and IgM rheumatoid factor (RF). Plain radiographs of pelvis, wrists, hands, and feet were performed in all cases.Anti-CCP were detected in 16/102 patients, 8/68 with symmetric polyarthritis, 1/8 with asymmetric polyarthritis, 2/20 with mono-oligoarthritis, 1/2 with mutilating arthritis, and 0/4 with exclusive axial or distal interphalangeal (DIP) involvement. The male:female ratio as well as frequency of dactylitis, enthesitis, and nonexclusive axial or DIP joint involvement were similar in the anti-CCP positive and negative groups. Anti-CCP positive patients were more frequently treated with disease modifying antirheumatic drugs and showed higher number of involved joints, and higher frequency of erosive arthritis and positive RF. Using multiple logistic regression, anti-CCP (but not RF) were significantly associated with erosive arthritis (odds ratio 9.8; 95% confidence interval 1.87-51.8) and > or = 10 involved joints (17.99; 3.6-89.2).Anti-CCP can be found in a small but significant proportion of patients with a clinical picture of PsA and are associated with erosive arthritis and multiple joint involvement.