AIM: To evaluate the efficacy of short-term overlap lamivudine therapy with adefovir in patients with lamivudine-resistant and naive chronic hepatitis B, we compared patients receiving overlap therapy with those receiving adefovir alone.METHODS: Eighty patients who had received lamivudine treatment for various periods and had a lamivudine-resistant liver function abnormality were enrolled. Forty of these patients received adefovir treatment combined with lamivudine treatment for ＞ 2 mo, while the other 40 received adefovir alone. We assessed the levels of hepatitis B virus (HBV) DNA at 0, 12 and 48 wk and serum alanine aminotransferase (ALT) levels after 0, 12, 24 and 48 wk of adefovir treatment in each group.RESULTS: We found serum ALT became normalized in 72 (87.5%) of the 80 patients, and HBV DNA decreased by ＞ 2 logio copies/mL in 60 (75%) of the 80 patients at the end of a 48-wk treatment. HBV DNA levels were not significantly different between the groups. The improvements in serum ALT were also not significantly different between the two groups.CONCLUSION: These findings suggest short-term overlap lamivudine treatment results in no better virological and biological outcomes than non-overlap adefovir monotherapy.