A Safety Study to Evaluate 12 Weeks of Treatment with Clevudine in Patients Infected with Hepatitis B Virus.

Inclusion Criteria: * HBV DNA positive with DNA levels at screening greater than or equal to 3,000,000 copies/mL. * Documented to be HBsAg positive for \> 6 months OR HBsAg positive and IgM anti-HBc negative and anti-HBs negative. Patients may be HBeAg positive, and anti-HBe negative OR HBeAg negative (pre-core mutant) and anti-HBe positive. * HBeAg positive and anti-HBe negative OR HBeAg negative (pre-core mutant) and anti-HBe positive with positive HBsAg for the previous 6 months * AST and ALT levels which are less than or equal to 10 times the upper limit of normal. * Bilirubin levels less than or equal to 1.5 x ULN or bilirubin levels \> 1.5 x ULN with diagnosis of Gilbert's disease and conjugated bilirubin within normal limits. Exclusion Criteria: * Currently receiving antiviral, immunomodulatory or corticosteroid therapy * Previous treatment with lamivudine, lobucavir, adefovir, famciclovir, or any other investigational nucleoside for HBV infection * Previous treatment with interferon must have ended at least 6 months prior to screening visit * History of ascites, variceal hemorrhage or hepatic encephalopathy * Co-infection with HCV or HIV * Evidence of cirrhosis or hepatocellular carcinoma (alpha fetoprotein)