AIM: To investigate the efficacy of combination treatment of IFN-α and lamivudine compared to lamivudine monotherapy, after 24 mo of administration in HBeAg-negative hepatitis B patients.METHODS: Fifty consecutive patients were randomly assigned to receive IFN-α-2b (5 MU thrice per week, n = 24) plus lamivudine (100 mg daily) or lamivudine only (n = 26) for 24 mo. Patients were followed up for further 6 mo. The primary outcome was the proportion with sustained virological response (undetectable serum HBV DNA concentrations) and or sustained biochemical response (transaminase levels within normal range) at 30 mo (6 mo after the end of therapy). Secondary end-points were timed from initial virological (biochemical) response to VBR (BBR, respectively) and the emergence of YMDD mutants across the two arms.RESULTS: Five of twenty-four (21%) patients in the combination arm vs 3/26 (12%) in the lamivudine arm had sustained response (i.e., normal serum transaminase levels and undetectable HBV DNA by PCR assay) 6 mo after treatment discontinuation. A reduction in the emergence of YMDD mutants and in the development of virological breakthroughs was observed in patients receiving combination treatment (10% vs46%, P= 0.01 and 14% vs46%, P= 0.03,respectively).Time from initial virologic response to virologic breakthrough (VBR) was greater among initial responders receiving combination treatment compared to those receiving lamivudine (22.9 mo vs 15.9 mo, respectively; P = 0.005).CONCLUSION: Our results demonstrate that IFN-α plus lamivudine combination therapy does not increase the sustained response, compared to lamivudine. However,combination therapy reduces the likelihood of VBR due to YMDD mutants and prolongs the time period until the breakthrough development.