The increasingly aggressive use of hepatitis B immune globulin (HBIg) in liver transplantation for hepatitis B infected patients has led to a great improvement in this procedure by lowering the incidence of allograft infection. In this article, major US studies on the use of HBIg are reviewed, including clinical results, clinical failures and problems, and the remaining information still needed for optimal therapy. Several major clinical findings have resulted from these studies. (1) With a high dose of HBIg and continuous use of this agent, it is possible to prevent recurrence in hepatitis B virus DNA-positive patients. (2) It is difficult to predict the required post-transplant dose of HBIg or the recurrence of hepatitis B in allografts. (3) While passive immunization of HBIg can help achieve successful transplants of patients suffering from hepatitis B cirrhosis, there are two typical patterns of failure: allograft infection with wild-type hepatitis B virus in the early perioperative period and with a mutant virus more than 6 months post-transplantation. These problems appear to arise only in patients with pre-transplant viral replication. (4) Combination therapy of HBIg and lamivudine seems promising for further improvement of liver transplantation. (5) There are still unanswered questions concerning the combination strategy: optimal timing, patient selection, duration of therapy, and the risk of viral mutations and adverse events. In addition, the role of changing immunosuppression protocols in improving transplantation of hepatitis B infected patients has not been determined.