Sera of patients with autoimmune liver disease contained antibodies reactive with nuclear lamins. These antigens were identified in immunoblotting experiments, using isolated nuclei, nuclear matrices, nuclear lamina-pore complexes and purified lamins as antigen source. The lamins were, furthermore, characterized by 2-dimensional gel electrophoresis. Antibodies to nuclear lamins were found in 75 per cent of the active lupoid hepatitis cases, but not in patients with inactive disease. Anti-lamin antibodies were detected in 8 per cent of primary biliary cirrhosis sera. The autoimmune liver disease sera recognized predominantly the nuclear lamins A/C, and less frequently the lamins A/B/C or lamin B.