The combination of lamivudine and hepatitis B immunoglobulin (HBIG) reduces the risk of hepatitis B virus (HBV) recurrence after liver transplantation (LT). However, the efficacy of this strategy and the need for combined therapy with adefovir dipivoxil (ADV) in patients who select lamivudine-resistant strains (YMDD) before surgery is still unknown. Twenty-two patients treated with lamivudine (LAM) who underwent LT after YMDD-mutant selection were studied. In 13 patients, YMDD mutants were associated with an HBV DNA breakthrough greater than 5 log10 (group A: phenotypic resistance), and 11 were treated with ADV to decrease viral load before LT. In the remaining 9 patients who did not experience the viral breakthrough, YMDD mutants were detected only retrospectively in sera stored at the time of LT (group B: genotypic resistance). During 35 months of post-LT follow-up, none of the 11 patients of group A treated with ADV before and after surgery (in addition to HBIG and LAM) had HBV recurrence, and neither did any of the 7 subjects of group B treated with LAM before and after transplantation (in addition to HBIG). HBV recurred in 2 patients of group A (untreated with ADV before surgery and transplanted with an HBV DNA exceeding 5 log10) and in 2 subjects of group B (who spontaneously stopped HBIG after surgery). In carriers of YMDD mutants, the risk of post-LT HBV recurrence is low, provided that preemptive and prophylactic ADV (in addition to LAM and HBIG) treatment is used in highly viremic patients and prophylactic LAM (or ADV) and HBIG therapy is continued in low viremic patients.