Serum ferritin levels in chronic liver diseases were measured by an enzyme-linked immunosorbent assay (ELISA) using two monoclonal antibodies (McAb) against placental ferritin. One of the McAbs (CM-H9) recognizes a specific placental-like isoferritin (PLF) only, while the other McAb (CM-G8) recognizes an isoform (CF) common to human placenta, liver and spleen. The different diseases studied were primary biliary cirrhosis (PBC-14 patients), chronic active hepatitis (CAH-12 patients), alcoholic cirrhosis (AC-18 patients) and cryptogenic cirrhosis (CRY-26 patients). Increased levels of both isoferritine were found in all these liver disorders, with an overall incidence of 80% for CF and 40% for PLF. The mean level of CF was significantly above normal in PBC, AC and CRY and that of PLF in PBC and CRY. Circulating placental-type isoferritins have not been previously described in patients with liver disorders. Our findings indicate that elevation of serum ferritin in liver diseases is caused by different isoferritin components.