Orthotopic liver transplantation (OLT) for hepatitis B virus (HBV) infection was limited until recently by poor graft and patient outcomes caused by recurrent HBV. Long-term immunoprophylaxis with hepatitis B immune globulin (HBIG) dramatically improved post-OLT survival, but recurrent HBV still occurred in up to 36% of the recipients. More recently, combination HBIG and lamivudine has been shown to effectively prevent HBV recurrence in patients post-OLT. The aim of the current study is to determine long-term outcome and cost-effectiveness of using combination HBIG and lamivudine compared with HBIG monotherapy in patients who undergo OLT for HBV. A retrospective chart review identified 59 patients administered combination HBIG and lamivudine and 12 patients administered HBIG monotherapy as primary prophylaxis against recurrent HBV. Lamivudine, 150 mg/d, was administered orally indefinitely. HBIG was administered under a standard protocol (10,000 IU intravenously during the anhepatic phase, then 10,000 IU/d intravenously for 7 days, then 10,000 IU intravenously monthly) indefinitely. A decision-analysis model was developed to evaluate the potential economic impact of prophylaxis against HBV with combination therapy compared with monotherapy. Recurrent HBV was defined as the reappearance of hepatitis B surface antigen (HBsAg) after its initial disappearance post-OLT. In the combination-therapy group, no patient redeveloped serum HBsAg or HBV DNA during mean follow-ups of 459 and 416 days, respectively. In the monotherapy group, 3 patients (25%) had reappearance of HBsAg in serum during a mean follow-up of 663 days. Combination therapy resulted in a dominant, cost-effective strategy with an average cost-effectiveness ratio of $252,111/recurrence prevented compared with $362,570/recurrence prevented in the monotherapy strategy. Combination prophylaxis with HBIG and lamivudine is highly effective in preventing recurrent HBV, may protect against the emergence of resistant mutants, and is significantly more cost-effective than HBIG monotherapy with its associated rate of recurrent HBV.