We investigated the presence of antinuclear antibodies (ANA) in 63 drug free and lithium treated bipolar patients as compared to 37 healthy controls. Increased frequency of positive ANA was detected in bipolar patients in comparison to controls (19% vs 5%, respectively, P < 0.05). This finding was unrelated to lithium treatment. No antinative DNA antibodies or antihistone reactive antibodies were detected among the ANA positive subjects.