Hepatitis C is an escalating global health problem. The recommended treatment regimen is associated with considerable expense, adverse effects and poor efficacy in some patients. Complementary therapies are widely promoted for and used by patients with hepatitis C. The aim of this project was to systematically assess the efficacy of complementary therapies in treating chronic hepatitis C. Systematic searches were conducted in six databases, reference lists of all papers were checked for further relevant publications and information was requested from experts. No language restrictions were imposed. A total of 27 eligible RCTs were located involving herbal products and supplements. No RCTs were identified for any other complementary therapy. In 14 of the trials, patients received interferon-alpha in combination with the complementary therapy. Less than half the trials (11/27) were of good methodological quality. Compared with the control group, significant improvements in virological and/or biochemical response were seen in trials of vitamin E, thymic extract, zinc, traditional Chinese medicine, Glycyrrhiza glabra and oxymatrine.