Objective To evaluate the long-term efficacy of consensus interferon in the treatment of chronic hepatitis C patients with genotype 1 who failed to respond to, or relapsed after, combination therapy with interferon alpha-2b and ribavirin. Design Open label pilot study. Methods Twenty-four chronic hepatitis C outpatient non-responders to (112 cases), or relapsers after (12 cases), standard combination therapy were treated with consensus interferon (9 mug five times per week) for 36 weeks. The patients were followed up for a further 24 weeks. The primary end-point of the study was the rate of sustained virological response. Results Sustained virological response was observed in 33% of previous non-responders and in 42% of previous relapsers. Improvement of the histological score was documented in 80% of previous non-responders and in all previous relapsers who showed undetectable levels of hepatitis C virus RNA at the end of treatment. Logistic regression analysis showed that sustained virological response was associated with a hepatitis C viral load of 2 x 10(6) copies/ml or less, with an inflammation score of 7 or less and with an estimated duration of disease of 10 years or less. The treatment was well tolerated with an 83% compliance. Conclusions Consensus interferon given at a dose of 9 mug five times per week for 36 weeks may offer a good chance of sustained virological response in a subset of patients who failed to respond to, or relapsed after, standard combination therapy. However, a larger randomized trial is required to assess the efficacy of consensus interferon before its use can be advocated for the treatment of such patients. (C) 2002 Lippincott Williams Wilkins.