Carbohydrate 19-9 antigen (CA 19-9) is considered a specific marker of pancreatobiliary adenocarcinomas, but slight increase of its levels can be found in several non-malignant diseases of the liver, such as autoimmune hepatitis. We describe a case of marked CA 19-9 elevation (up to 898.0 U/ml) in a patient with autoimmune hepatitis. Laboratory and instrumental examinations excluded malignant diseases. Immunohistochemical analysis for CA 19-9 and MIB-1, performed on liver biopsy, showed reactivity in inflammatory areas, in particular in bile ductule cells and hepatocytes in ductular metaplasia, suggesting that these cells could be involved in CA 19-9 serum levels increase. After steroids, the clinical picture improved and all the laboratory parameters normalised.