Chronic hepatitis B virus (HBV) infection is still a major cause of liver disease for which no definite therapy is available. We describe here a hepatitis B surface antigen (HBsAg) carrier patient with active viral replication (HBV DNA positive) who was treated for leukemia by bone marrow transplantation (BMT) from an HBV immune donor. Following BMT from the antibody to hepatitis B core antigen (anti-HBc) positive/anti-HBs positive bone marrow donor, immune reconstitution of the recipient's bone marrow resulted in clearance of the circulating HBsAg, as well as HBV DNA. The patient acquired immunity against HBV, which lasted for more than 8 months posttransplantation. Therefore, this report provides evidence that adoptive transfer of specific immunity against HBV through allogeneic BMT may lead to clearance of persistent HBV infection. Furthermore, the data support the hypothesis that the HBsAg carrier state is most probably the result of an inefficient immune response against HBV, implying that clearance of HBV may be facilitated by adoptive cellular immunotherapy.