This is a randomized, open-labelled, prospective 96-week study comparing the antiviral efficacy and safety of switching to entecavir 0.5mg QD from lamivudine versus maintaining lamivudine 100mg QD treatment in CHB patients currently receiving lamivudine monotherapy.

Entecavir has a higher potent antiviral efficacy and a lower drug resistance rate than those of Lamivudine in nucleoside-naïve CHB patients. The switch from Lamivudine to Entecavir in patients who have undetectable hepatitis B virus DNA (HBV DNA < 60 IU/mL) may lead to more prolonged viral suppression to undetectable level by PCR method, compared to patients with continuous lamivudine treatment. The results of this study will provide a rationale for switch treatment from one antiviral to another one, especially from LAM to ETV.

Inclusion Criteria:

• Adult subjects (18-70 years of age) currently taking lamivudine monotherapy for chronic HBV infection for at least 6 months with < HBV DNA 60 IU/mL level and HBeAg positive status.

Exclusion Criteria:

• Subjects treated with other antiviral drugs (e.g. adefovir) in combination with lamivudine are not eligible for this study.
• Subjects should have ALT < 10 x ULN, and no evidence of hepatocellular carcinoma.
• Subjects should be without serological evidence of co-infection with HCV, HIV, or HDV.
• Subjects with decompensated liver disease, as well as pregnant or breast-feeding women, will not be eligible for the study.