KEY INCLUSION CRITERIA:

   - Age 18 years or older

   - All genders and ethnicity

   - Positive HBsAg

   - HBeAg positive and negative

   - Pretreatment HBV DNA of 10,000 copies/mL or higher (for purposes of this study, both
   copies and equivalent IU measurements will be recorded and analyzed)

   - Patients who are switched to, or prescribed, entecavir after treatment with adefovir
   for at least 12 weeks by the providing physician.

   - Patients with and without prior lamivudine exposure will be enrolled but enrollment of
   lamivudine experienced cases will be limited to no more than 30 patients total

KEY EXCLUSION CRITERIA:

   - Patients who refused to consent to the study

   - Patients younger than 18

   - Vulnerable subjects such as pregnant women, prisoners, employees, patients with
   significant cognitive deficits.

   - Patients with prior exposure to another nucleoside for more than 2 weeks. Those with
   prior exposure to lamivudine will be enrolled under conditions detailed above.

   - HIV co-infection

   - HCV co-infection

   - HDV co-infection

   - Recipients of solid organ transplantation

   - Patients who receive high-dose steroid (60 mg/d or higher and for longer than 10 days)