The purpose of this clinical research study is to assess the safety and effectiveness of switching to entecavir compared to continued lamivudine in patients with chronic hepatitis B.

• Male and female subjects =/> 16 years of age (or minimum age required in a given country) with history of HBeAg-positive chronic hepatitis B infection;
• Incomplete response to current lamivudine therapy;
• HBeAg-positive;
• Absence of coinfection with human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis D virus (HDV);
• Absence of other forms of liver disease e.g., alcoholic, autoimmune, biliary disease.