This study will evaluate the efficacy and safety of 4 regimens of PEGASYS plus Copegus, in patients with chronic hepatitis C (CHC) genotype 1 who have failed to respond to previous treatment with standard doses of PEGASYS plus ribavirin. Patients will be randomized to one of 4 groups, to receive a)PEGASYS 360 micrograms/week plus Copegus 1000-1200mg/day, b)PEGASYS 180 micrograms twice weekly plus Copegus 1000-1200mg/day, c)PEGASYS 360micrograms/week plus Copegus 1200-1600mg/day, or d)PEGASYS 180 micrograms twice weekly plus Copegus 1200-1600mg/day. Following 48 weeks treatment, there will be a 24 week period of treatment-free follow-up. The anticipated time on study treatment is 3-12 months, and the target sample size is 100-500 individuals.

Inclusion Criteria:

• adult patients >=18 years of age, with CHC genotype 1;
• patients who have failed to respond to previous treatment with PEGASYS plus ribavirin for >=12 weeks;
• patients who have discontinued PEGASYS/ribavirin >=4 weeks prior to enrollment;
• compensated liver disease.

Exclusion Criteria:

• other forms of liver disease;
• infection with HIV, HAV, HBV;
• hepatocellular cancer.