Hepatitis B accounts for approximately 5000 deaths per year in the United States. Liver transplantation offers the only hope for patients who develop end-stage liver disease. Early results of liver transplantation for hepatitis B were poor with recurrence rate of 80% and 1-year survival of only 50%. Recent studies found that preventive therapy using hepatitis B immune globulin (HBIG) or antiviral medications such as lamivudine can reduce the recurrence rate to roughly 30% with accompanying improvement in survival. However, HBIG when given as intravenous infusion in high doses is very expensive, while long-term use of lamivudine is associated with drug resistance. Some studies found that preventive therapy using both HBIG and lamivudine may decrease recurrence rate to less than 10% but the dose and duration of HBIG needed when used in combination with lamivudine is not clear. Adefovir, a new antiviral medication, is effective against lamivudine resistant hepatitis B but its role in liver transplantation is uncertain because of the risk of kidney damage. Many studies showed that the risk of recurrent hepatitis B is related to the viral load before transplant. Thus, it may be possible to tailor the preventive therapy according to the risk. The aim of this study is to establish the most cost-effective preventive therapy for recurrent hepatitis B after liver transplantation.