Patients with autoimmune chronic active hepatitis (AICAH) often have very high titres of antibodies to rubella and/or measles virus. In the present study a young girl at the clinical onset of AICAH exhibited very high titres of antibodies against influenza viruses A and B, parainfluenza viruses, rubella virus and varicella-zoster virus, The titres normalized over 2 months except for rubella and varicella-zoster antibodies. Strong reactivities were seen against the rubella structural proteins E1, E2 and C in Western blot but IgM antibodies were not demonstrated. Total IgG was increased with normal ratios of subclasses. The IgG 1 was the dominant antibody to El and E2, while IgG4 dominated the anti-C response, There was no significant shift in subclass reactivities over one year from onset, The polymerase chain reaction (PCR), using a nested primer set, was negative for rubella virus RNA in a liver biopsy obtained at the clinical onset and in peripheral blood mononuclear cells (PBMC) 1 year later. Go-cultivation experiments using PBMC and permissive cell lines were also negative for rubella virus. Hence, in the very early phase of AICAH there may be a transiently enhanced antibody response to various unrelated viruses.