BACKGROUND/AIMS: this study aimed to determine the viremia status after clinical, biochemical and serological recovery from acute hepatitis B viral (HBV) infection. METHODS: we detected serum HBV-DNA in 19 patients with acute hepatitis B during followed-up 6-43 months after onset, and analyzed HBV genotypes. RESULTS: 13 (72%) of 19 patients had detectable HBV DNA at the point of 6 months after onset, and four (33%) of 12 patients had persisted viremia for more than 1 year although they were recovery with normalization of alanine transaminase (ALT), disappearance of hepatitis B surface antigen (HBsAg) and appearance of antibody against HBsAg (anti-HBs). Eighteen (95%) of 19 patients were infected with HBV genotype C, one (5%) with genotype B. CONCLUSIONS: these results suggest genotype C of HBV is the predominant genotype of acute hepatitis B in Nagasaki region in Japan. HBV can persist in the serum for more than one year after complete clinical and serological recovery from acute viral hepatitis.