Inclusion Criteria:

• 18 through 69 years of age, inclusive
• Chronic HBV infection, defined as positive serum HBsAg for at least 6 months

• Active chronic HBV infection with all the following:

  1. Currently treated with adefovir dipivoxil 10 mg QD (for at least 24 weeks but not more than 72 weeks)
  2. HBeAg positive or negative at screening
  3. Serum HBV DNA greater than 100,000 copies/mL for HBe Ag positive OR serum HBV DNA greater than 10,000 copies/mL for HBe Ag negative at screening
  4. Serum ALT less than 10 times the upper limit of normal
  5. Calculated creatinine clearance of at least 70 mL/min using the Cockcroft-Gault formula.
  6. Hemoglobin at least 8 g/dL
  7. Neutrophils at least 1,000 /mm3
• Nucleoside-naïve or lamivudine-experienced
• Negative serum beta-HCG
• Compliant with adefovir dipivoxil
• Willing and able to provide written informed consent.

Exclusion Criteria:

• Pregnant women, women who are breastfeeding or who believe they may wish to become pregnant during the course of the study.
• Male or females of reproductive potential who are unwilling to use an effective method of contraceptive while enrolled in the study. For males, condoms should be used and for females, a barrier contraception method should be used.
• Decompensated liver disease defined as conjugated bilirubin greater than 1.5 times ULN, prothrombin time (PT) greater than 1.5 times ULN, platelets less than 75,000/mm3, serum albumin less than 3.0 g/dL, or prior history of clinical hepatic decompensation (e.g., ascites, jaundice, encephalopathy, variceal hemorrhage).
• Prior use of tenofovir DF or entecavir
• Received treatment with interferon or pegylated interferon within 6 months of the screening visit.
• Evidence of HCC; for example, alpha-fetoprotein greater than 50 ng/mL or by any other standard of care measure.
• Co-infection with HCV (based on serology), HIV, or HDV.
• Significant renal, cardiovascular, pulmonary, or neurological disease.
• Received solid organ or bone marrow transplantation.
• Is currently receiving therapy with immunomodulators (e.g., corticosteroids, etc.), investigational agents, nephrotoxic agents, or agents capable of modifying renal excretion.
• Has proximal tubulopathy
• Known hypersensitivity to the study drugs (tenofovir DF or emtricitabine/tenofovir DF), the metabolites (tenofovir or emtricitabine) or formulation excipients.