In this open-label multicenter study the long-term effect of Pegasys monotherapy on pharmacodynamic HBV-related markers will be investigated in patients with chronic hepatitis B. Eligible patients will have completed treatment on another donor protocol (e.g. PP22512) and will receive Pegasys at an appropriate dose based on the standard of care (180mcg sc once weekly) for up to 48 weeks. Target sample size is <100.

Inclusion Criteria:

• adult patients >/=18 years of age
• previous participation in other donor protocol
• chronic hepatitis B
• no other anti-HBV treatment after completion of previous donor protocol
• female patients and female partners of male patients must use at least two methods of contraception until 28 days after completion of study

Exclusion Criteria:

• hepatic decompensation (Child-Pugh class B and C)
• antiviral, antineoplastic or immunomodulatory treatment
• evidence of alcohol and/or drug abuse