This randomized, double-blind, placebo-controlled study will evaluate the efficacy and safety of setrobuvir in patients with genotype 1 chronic hepatitis C. Treatment-naïve patients will be randomized to receive either setrobuvir (800 mg orally b.i.d loading dose followed by 200 mg orally .b.i.d.) or placebo in combination with standard of care Pegasys (peginterferon alfa-2a) and Copegus (ribavirin). Treatment duration will be 28 weeks or 48 weeks depending on response. Treatment-experienced patients categorized as relapsers, partial responders and viral breakthrough patients to previous pegylated interferon and ribavirin therapy will be randomized to receive either setrobuvir or placebo in combination with Pegasys and Copegus for 48 weeks. Treatment-experienced patients categorized as null-responders to previous pegylated interferon and ribavirin therapy will be assigned to treatment with setrobuvir plus Pegasys and Copegus for 48 weeks.

Inclusion Criteria:

• Adult patients, 18 to 65 years of age inclusive
• Documented chronic hepatitis C
• Treatment-naïve (no prior exposure to Pegasys, Copegus, or experimental HCV therapy) or treatment-experienced with current standard of care (Pegasys and Copegus) but categorized as null-responder or patients with partial response, relapse or viral breakthrough during or following prior treatment
• Serum HCV RNA >/= 50,000 IU/mL at screening
• HCV antibody positive at screening
• HCV genotype 1
• Body mass index (BMI) 18-38 kg/m2
• In good health other than chronic HCV infection in the judgment of the principal investigators
• Negative for hepatitis B and HIV infection

Exclusion Criteria:

• Pregnant or breastfeeding women
• For treatment-naïve patients: any previous treatment for HCV infection
• For treatment-experienced patients: previous treatment with an experimental therapy for HCV infection
• Co-infection with HIV or hepatitis C virus (HBV)
• History or evidence of decompensated liver disease
• History or evidence of hepatocellular carcinoma
• History of alcohol abuse and/or other drug addiction \