This 4 arm study will compare the efficacy and safety of PEGASYS given for 24 or 48 weeks, and at doses of 90 or 180 micrograms weekly, in the treatment of HBeAg positive patients with chronic hepatitis B. Patients will be randomized to one of 4 treatment groups: a)PEGASYS 90 micrograms subcutaneous (sc) weekly for 24 weeks, b)PEGASYS 180 micrograms sc weekly for 24 weeks, c)PEGASYS 90 micrograms sc weekly for 48 weeks or d)PEGASYS 180 micrograms sc weekly for 48 weeks. Following treatment there will be a 24 week period of treatment-free follow-up in all treatment groups for the primary endpoint. The anticipated time on study treatment is 3-12 months, and the target sample size is 500+ individuals.