Conventional interferon (IFN) alfa has been used for many years in the treatment of chronic hepatitis C. However, few patients achieve sustained virological responses with IFN. Combining IFN with ribavirin improves efficacy considerably, but at the expense of diminished tolerability attributable to ribavirin. Pegylated interferons have improved pharmacokinetic profiles, may be administered once weekly, and are more effective than IFN is alone or in combination with ribavirin. In addition to enhanced efficacy, pegylated interferon alfa-2a (40 kD) also improves health-related quality of life during therapy compared with IFN-based therapy. New adjuvant agents have the potential to further improve sustained response rates and tolerability; however, pegylated interferons will likely remain the backbone of therapy in the foreseeable future. Therapies under development and evaluation for patients with HCV infection include adjunctive use of the antiviral agent amantadine and the immunomodulatory agent thymalfasin. Novel small molecules include the ribavirin analogues, viramidine and levovirin, and BILN 2061, an inhibitor of HCV serine protease. Other therapeutic strategies that have reached the clinic include antisense oligonucleotides (ISIS 14803), nuclease-resistant ribozymes targeting HCV RNA (Heptazyme), human monoclonal antibodie, and human antibody fragments directed at HCV helicase.