Objective To investigate the risk factors of hepatitis B virus(HBV) re-infection after orthotopic liver transplantation(OLT)and to evaluate the therapeuticefficacy of hepatitis Bimmunoglobulin(HBIG)combined with nucleos(t)ide analogues. Methods The study included 160 patients with HBVrelated liver diseaseswho underwent OLT in the Third Affiliated Hospital of Sun Yat-sen University from October 2003 to Augest 2007, 117 of whom were treated with nucleos(t)ide analogues before OLT;and all patients were received HBIG i. m and nucleos(t)ide analogues treatment after OLT. Preoperative data of the patients were retrospectively reviewed, and HBV re-infection was assessed prospectively. Independent t test was used to compare normally distributed data and Fisher's exact test was used for the comparison of rates among groups. Results HBV re-infection Was observed in 19 patients after OLT with a rate of 11. 88%(19/160), which was not correlated with HBV DNA loads, HBeAg and the duration of antiviraltherapy before OLT(r=0.108, 0.127 and 0.033, P>0.05). Of 19 patients with HBV re-infection, 17 were treated with lamivudine after OLT, and HBV YMDD mutants were detected in 8. The YMDD positive group had a higher HBV DNA level than YMDD negative group(7.0 ± 2.0 log copies/mL vs 3.2 ± 2.5 log copies/mL, t = 3.531, P=0.003). Among above 17 patients, 12 received adefovir add-on treatment, and3 received entecavir instead of lamivadine; all achieved satisfactory responses. Conclusions Low dose of HBIG combined with long-term use of nucleos(t)ide analogues can effectively prevent HBV re-infection after OLT. HBV YMDD mutation may be the primary reason for HBV re-infection in the patients treated with lamivudine after OLT.