Switching Study From Lamivudine to Clevudine in the Chronic Hepatitis B Patients

Inclusion Criteria: * HBV DNA \> 2,000 copies/mL at screening * Patients who have compensated liver disease (Child-Pugh score =\<6) * Patients without LMV resistant mutation by RFMP assay * Patients who have NOT experienced viral breakthrough at consecutive two measurements (at least one month apart) during lamivudine monotherapy * Patients who can submit the written consent and comply with the claims postulated of this clinical trial Exclusion Criteria: * Currently receiving antiviral except LMV or corticosteroid therapy * Patients that previously received antiviral treatment for hepatitis B other than lamivudine in the proceeding 12 months * Previous treatment with interferon or other immunomodulatory therapies must have ended at least 6 months preceding the study screening * Treatment with nephrotoxic drugs, competitors of renal excretion, and/or hepatotoxic drugs within 2 months before study screening or during the study period * Patients who is co-infected with HCV, HDV or HIV * Serious concurrent medical conditions * Prior organ transplantation * Patient has creatinine clearance less than 60mL/min as estimated by the following formula: \[(140-age in years) (body weight \[kg\])\] / \[(72) (serum creatinine\] \[mg/dL\])\[Note: multiply estimates by 0.85 for women\]