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.