The combined therapy with interferon with or without pegylation associated with ribavirin has shown greater sustained virological response than monotherapy with interferon-alpha, however this response still represents around 60% of cases. The mechanisms by which HCV causes cellular damage are not yet well understood, however immune liver damage, direct cytotoxic damage mediated by different viral products and also oxidative stress have been implicated in the pathogenesis of chronic hepatitis C. Several studies support that reactive oxygen species (ROS) and oxidative stress are involved in the pathogenesis of hepatitis C, despite that increased ROS levels in HCV patients might be beneficial by suppressing HCV replication. ROS are involved in several diseases and cause oxidative damage to lipids, DNA, proteins and carbohydrates.