Since the introduction of famciclovir in the treatment of hepatitis B virus (HBV) infection after liver transplantation, promising results have been published. In this study, the long-term efficacy and safety of famciclovir were assessed. Twenty-four patients with recurrent hepatitis B and 6 patients with de novo infection after liver transplantation were enrolled in an open prospective trial. Patients received oral famciclovir, 500 mg three times daily. Serum HBV-DNA, viral serology, and liver enzymes were measured sequentially; liver histology was taken before and during treatment in 12 patients. In the reinfected patients, 17 patients initially responded well to treatment, with a mean decrease of HBV-DNA of 82%, 5 patients became HBV-DNA negative. The drug was effective for 1-51 months (mean 16 months), then viral replication increased again in 13 out of 17 patients. One patient did not respond to treatment. Six out of 24 patients already had severe cirrhosis at the time of enrollment and died shortly afterwards, due to the HBV infection. The 6 patients with de novo infection all had a decline of HBV-DNA for 2-42 months (mean 14 months); 1 patient converted to HBV-DNA negative. Five out of 6 patients experienced a viral breakthrough later on. No severe side-effects were observed. Therefore, famciclovir is effective in certain HBV-infected patients after orthotopic liver transplantation (OLT), but in the long term, most of the patients relapse.