BACKGROUND/AIMS: The aim of this study was to compare the efficacy of lamivudine therapy between chronic hepatitis B (CHB) patients, whose ALT levels less than 2 times the upper limit of normal (ULN) and patients whose ALT levels are more than 2 times ULN. METHODS: We retrospectively analyzed 508 consecutive patients with HBeAg-positive CHB who were treated with lamivudine for 1 year or more. Forty-six patients (Group A) with pretreatment ALT levels less than 2 times ULN were retrospectively compared with 462 patients (Group B) whose ALT levels are more than 2 times ULN. RESULTS: HBeAg seroconversion was achieved in 15 (32.6%) of group A and 162 (35.1%) of group B. The cumulative rates of HBeAg seroconversion in group A and B were 19% and 21% at 12 months; 35% and 31% at 24 months; and 38% and 39% at 36 months, respectively. HBV breakthrough was observed in 20 (43.5%) of group A and 192 (41.6%) of group B. The cumulative breakthrough rates of group A and B were 18% and 12% at 12 months; 33% and 29 % at 18 months; 45% and 42% at 24 months, respectively. Post-treatment relapse in group A and B occurred in 56% (5/9) and 41% (44/108), respectively. Therefore, the rates of the HBeAg seroconversion, breakthrough, and post-treatment relapse were not significantly different between these two groups. CONCLUSIONS: Lamivudine therapy in HBeAg-positive CHB patients whose ALT levels are minimally elevated is as effective as in treatment of the patients whose pretreated ALT levels are twice more than ULN.