OBJECTIVE To evaluate the prevalence and clinical correlations of antibodies against Saccharomyces cerevisiae (ASCA) among patients with BD. METHODS Twenty-seven BD patients were studied. Data from medical files and from patients' interviews was collected, regarding the entire spectrum of disease manifestations, and a severity score was calculated for each patient. IgA- and IgG-ASCA levels, determined by ELISA, were studied in all BD patients and in three control groups: patients with recurrent aphthous stomatitis (RAS), systemic lupus erythematosus (SLE) and healthy volunteers. RESULTS Thirteen BD patients (48.1%) were ASCA-positive, compared to one patient in each control group (10%, p = 0.01). The mean value of IgG-ASCA in the BD patients was 20.7 +/- 12.3 units, significantly higher than in patients with RAS (10.0 +/- 5.5, p < 0.001), SLE (11.8 +/- 9.3, p < 0.03) or healthy volunteers (10.8 +/- 9.8, p < 0.02). Mean IgA-ASCA level was 16.8 +/- 8.8 units in the BD patients, significantly higher compared to healthy volunteers (11.0 +/- 5.0, p = 0.02) but similar to patients with RAS (17.0 +/- 5.3). No correlation was found between ASCA and any BD-associated clinical manifestation nor the presence of HLA-B5. No difference was found in the rate of major oral ulcers nor in the systemic disease severity score between positive- and negative-ASCA patients (27.3% vs. 30.8%, and 7.31 +/- 1.80 vs. 7.28 +/- 2.27 respectively, NS). CONCLUSIONS The results of our study associate, for the first time, the presence of a distinct antibody, i.e. ASCA, with BD. ASCA were not linked to a specific clinical manifestation of the disease and probably do not pose an increased risk for a more severe disease course.