The aim of our study was to assess the efficacy and safety of entecavir in kidney- and liver-transplant recipients with chronic hepatitis B virus (HBV) infection. Ten male transplant patients with chronic HBV infection (eight kidney- and two liver-transplant patients), who have become adefovir (n=9) or lamivudine-resistant (n=1) were given entecavir at 0.5 to 1 mg/d. All patients were HBs Ag positive: six were HBe Ag(-)/HBe Ab(+), and four were HBe Ag(+)/HBe Ab(-). After a median follow-up of 16.5 months, entecavir therapy was associated with a significant decrease in HBV DNA viral load, that is, 3.86 (2.71-6.46) log10 copies/mL at baseline down to 2.94 (2.15-4) log10 copies/mL at last follow-up (P=0.004). Rate of HBV DNA clearance was 50% in both HBeAg(+) and HBeAg(-) patients. There were no significant changes in renal function or hematological parameters. This study demonstrates that entecavir therapy is safe and efficient in HBV(+) organ-transplant patients.