We have treated 19 HBV carriers who developed acute severe exacerbation using interferon and immunosuppressive agents. Of these 14 patients developed fulminant hepatic failure. Of 10 patients with positive result for serum HBV DNA polymerase before the start of te treatment, five patients in whom HBV DNA polymerase turned negative and one patient whose HBV DNA polymerase level fluctuated in a low abnormal range after the start of the treatment survived. While, four patients whose HBV DNA polymerase level remained high after the start of interferon treatment died. Thus, it is suggested that suppression of HBV virus replication is closely related to prognosis in HB carriers developing acute severe exacervation of hepatitis.