Antibodies to the baker's yeast Saccharomyces cerevisiae (ASCA), recently proposed as a serological marker of Crohn's disease, have also been detected in other autoimmune disorders. The aim of this study was to determine prevalence and clinical significance of ASCA in autoimmune liver disease. The presence of IgG and IgA ASCA was evaluated using a commercially available immunoassay in 215 patients with autoimmune liver disease (primary biliary cirrhosis, PBC, 123 cases; autoimmune hepatitis, AIH, 67 cases; primary sclerosing cholangitis, PSC, 25 cases), 48 with inflammatory bowel disease and 19 healthy blood donors. Anti neutrophil cytoplasmic antibodies with the perinuclear pattern (p-ANCA) were assessed by indirect immunofluorescence in PSC patients. The main clinical and biochemical parameters between ASCA-positive and negative patients were analysed and compared. ASCA are predominant in Crohn's disease (70%); among liver patients, PSC and AMA-negative PBC show the highest ASCA prevalence (53% and 44%). In PBC ASCA correlate with higher levels of circulating IgA (P < 0.05). In PSC the detection of either ASCA or p-ANCA is neither associated with any clinical or biochemical feature, nor with an underlying inflammatory bowel disease. ASCA can not be considered an additional serological marker of autoimmune liver disease, but the possibility of detecting such a reactivity in autoimmune liver disorders should be considered; their correlation with elevated IgA in PBC suggests that ASCA may be an indirect sign of enhanced mucosal immunity; in PSC patients neither ASCA nor p-ANCA predict the occurrence of a concomitant inflammatory bowel disease.