Abstract Asymptomatic chronic hepatitis B virus (HBV) carriers are at risk of developing complications of liver disease, but these patients are not recommended for treatment with antiviral drugs. In fact, antiviral drugs are ineffective in these patients in the immune tolerance phase, when they have inadequate levels of host immunity. We postulated that combination therapy of an immune modulator and antiviral drugs may have potential to help these patients. Twenty-five patients with incidentally-detected asymptomatic chronic HBV were immunized with hepatitis B vaccine (10 microg of hepatitis B surface antigen) intramuscularly five times (at 0, 1, 2, 6, and 12 mo) to induce HBV-specific immunity. The patients were also treated with lamivudine (100 mg) daily for 12 mo. The combination therapy was safe for all patients with asymptomatic chronic HBV, and no increases in alanine aminotransferase or liver damage were detected in any patient. Although all of the patients were expressing HBV DNA in their serum before treatment, HBV DNA became undetectable in 16 of 25 patients, and was reduced in 9 of 25 patients at the end of the combination therapy. Combination therapy with the antiviral agent lamivudine and an immune modulator (hepatitis B vaccine) represents a potential therapeutic option for the control of HBV without liver damage in asymptomatic chronic HBV carriers.