We tested serum samples from 48 patients with Psoriatic Arthritis (PA) for Antinuclear Antibodies (ANA) using a highly sensitive substrate (Hep-2 cells). We obtained the following results: 1) in PA patients ANA positivity (16.6%) was significantly higher than in age-and sex-matched groups of healthy controls (4.1%; p less than 0.05) and uncomplicated psoriasis (2%; p less than 0.025). 2) ANA were more common in Symmetrical Polyarthritis (37.5%) and Arthritis Mutilans (25%) than in Asymmetrical Oligoarthritis and Spondarthritis (11.8%) and 'Classical' PA (0%). 3) We did not find any positivity for anti-DNA and anti-ENA antibodies among PA patients.