As part of an investigation into the question of whether virus-induced autoreactivity might contribute to liver damage in viral hepatitis, serial studies (from onset through recovery) of circulating liver autoantibodies have been performed in patients with uncomplicated acute virus A (AVH-A), B (AVH-B) and non-A, non-B (AVH-NANB) hepatitis in whom the time of onset of symptoms could be precisely documented. One hundred and forty-four sera from 35 patients were tested by radioimmunoassay for autoantibodies against the liver-derived lipoprotein complex, LSP, and also against one of its constituents--the asialoglycoprotein receptor, known as hepatic lectin (HL). Anti-LSP antibodies were found in all 10 patients with AVH-A, in 17/18 with AVH-B and in 3/7 with AVH-NANB at titres that declined during recovery. Anti-HL antibodies were detected concurrently in 6 of the AVH-A patients and in 5 with AVH-B but on only 1 occasion in 1 patient with AVH-NANB. Transient cellular immunity to LSP, assayed by a T-lymphocyte migration inhibitory factor test, was detected in 4 of the 6 AVH-B patients tested, 2 of whom also showed concurrent reactivity to HL, but these cellular immune responses did not correlate with production of anti-LSP and/or anti-HL. The findings indicate that humoral immune responses to liver cell surface antigens are frequently triggered by hepatitis A and B viruses, possibly via induction of autoreactive, T-cell independent, liver antigen-specific B lymphocytes. These liver-specific autoreactions have the potential to contribute to hepatocellular damage in virus A and B hepatitis but it seems unlikely that autoimmunity plays a significant pathogenetic role in NANB viral infections.