Analysis of HBV-Specific Immune Response in Patients With HBeAg Negative Chronic Hepatitis B Treated With Pegasys (Peginterferon Alfa-2a (40KD)) - Immunology Sub-Study of ML18253

Inclusion Criteria:

• Adult patients 18-55 years of age

• Chronic HBeAg negative hepatitis B

• Liver disease consistent with chronic hepatitis documented by liver biopsy within 18months prior to enrollment

• Participation in study ML18253.

Exclusion Criteria:

• Interferon-based or any systemic anti-HBV therapy </= 12 months prior to first dose ofstudy drug

• Antiviral, anti-neoplastic, or immunomodulatory treatment </= 12 months prior to firstdose of study drug

• Nonresponders to previous interferon therapy and resistant to lamivudine

• Co-infection with hepatitis A, C or D, or with human immunodeficiency virus (HIV)

• Hepatocellular cancer

• Compensated (Child A, score 6) or decompensated liver disease (Child B or C)

• History or evidence of medical condition associated with chronic liver disease otherthan HBV