This is a treatment protocol to evaluate the antiviral efficacy, safety and tolerability polyethylene glycol (PEG) conjugated interferon alfa-2b (PEGIntron) for the treatment of chronic hepatitis C virus infection in patients who have previously failed to achieve a sustained virologic response following interferon alfa or interferon alfa-2b plus ribavirin therapy. Patients will be stratified according to their response to the previous course of therapy (i.e. non-reponse or relapse virologic pattern