We report a case of living-related partial liver transplantation for decompensated hepatitis B without reactivation of hepatitis B in the following 30 months, and we analyze the factors that indicate a favorable prognosis for transplantation. The 42-year-old female patient received continuously administered lamivudine before transplantation, and hepatitis B virus immunoglobulin (HBIG) from the anhepatic phase to the present. Currently, she shows a normal aminotransferase level and is negative for hepatitis B surface antigen and hepatitis B virus (HBV) DNA by polymerase chain reaction amplification. Sequence analysis was performed. The entire precore/core region and part of the polymerase region of HBV were sequenced by a direct sequencing method after polymerase chain reaction. No specific mutation was found in these regions. These observations show that the key factors in the long-term successful treatment of this patient appear to be the combination therapy of lamivudine and HBIG that the patient received from around the time of the transplantation. Furthermore, the lack of specific mutations, including lamivudine resistant-mutations, is likely to represent an additional factor in the effectiveness of this treatment.