About 60% to 85% of people infected with hepatitis C virus will go on to develop chronic hepatitis C, which is now believed to affect 3% of the world's population.We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions in treatment-naïve people with chronic hepatitis C infection, but without liver decompensation? What are the effects of interventions in people with chronic hepatitis C infection, but without liver decompensation, who have not responded to interferon treatment? What are the effects of interventions in people with chronic hepatitis C infection, but without liver decompensation, who relapse after interferon treatment? What are the effects of interventions in people with chronic hepatitis C infection who also have HIV? We searched: Medline, Embase, The Cochrane Library, and other important databases up to April 2008 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the FDA and the UK Medicines and Healthcare products Regulatory Agency (MHRA).We found 35 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.In this systematic review we present information relating to the effectiveness and safety of the following interventions: interferon monotherapy; interferon alfa plus ribavirin; peginterferon monotherapy; and peginterferon plus ribavirin.