Liver transplantation in HBs-antigen (HBsAg) positive allograft recipients is associated with a high risk of HBV recurrence some time after surgery. So far, results of measures to prevent recurrent HBV-infection by means of treatment with interferon, hepatitis B vaccination and short-term passive immunization with hepatitis B immunoglobulin (HBIg) or monoclonal antibody to HBsAg (anti-HBs) have been disappointing. In the present study the results of long-term, anti-HBs monitored passive immunization with HBIg is reported. In 23 HBsAg-positive liver transplant recipients an anti-HBs level of greater than or equal to 100 IU/l was maintained for 6 or 12 months, respectively. The rate of recurrent infection was found to be less than 20% under HBIg substitution, whereas 11 graft recipients with no or only short-term HBIg prophylaxis were reinfected by month 15 after transplantation. HBV recurrence was associated with chronic liver disease and recurrent cirrhosis in the allograft.