In this randomized, cross-over, open label study the correlation of Pegasys (peginterferon alfa-2a) pharmacokinetics after intravenous (iv) and subcutaneous (sc) administration with viral load and viral kinetics will be investigated in patients with chronic hepatitis C genotype 1 who were non-responders to previous standard combination therapy with pegylated interferon and ribavirin. Patients will be randomized to receive either weekly or twice weekly Pegasys iv or sc for 2 weeks, crossing over to the other mode of administration after a washout period of 6 weeks.

Inclusion Criteria:

• Adult caucasian patients, 18 - 70 years of age
• Hepatitis C, genotype 1
• Non-responder to previous anti-HCV therapy with peginterferon alfa and ribavirin
• Compensated liver disease (Child-Pugh class A) for >/= 24 months before baseline
• Positive for anti-HCV for > 6 months, with detectable serum HCV-RNA

Exclusion Criteria:

• Treatment-naïve or responder to previous therapy
• HCV infection other than genotype 1
• Positive for Hepatitis A, Hepatitis B or HIV infection at screening
• Chronic Hepatitis of other than HCV origin
• Decompensated liver disease (Child-Pugh class B or C)
• Therapy with systemic antiviral, antineoplastic or immunomodulatory agents in the 6 months prior to study
• Clinically relevant retina disorder
• Pregnant or lactating women and male partners of pregnant women