The risk of severe hepatic damage due to reactivation of hepatitis B virus (HBV) infection after intensive myelosuppressive chemotherapy is well known. Two of the most evolved nucleotide analogues showing good activity against the hepatitis B virus are lamivudine and famciclovir. We report the successful therapeutic use of lamivudine and famciclovir for fulminant reactivated hepatitis B after autologous peripheral blood stem cell transplantation (PBSCT) and the subsequent prophylactic use of lamivudine during allogeneic blood stem cell transplantation (alloSCT) for chronic lymphocytic leukemia (CLL) in a 40-year-old patient. Antiviral therapy was well tolerated and no hematotoxicity occurred. Our observation warrants further investigation of antiviral therapy with famciclovir and lamivudine in HBV carriers receiving intensive myelosuppressive chemotherapy.