The combinations of peginterferon alfa-2a or peginterferon alfa-2b with ribavirin lead to significant improvement in sustained virological response when compared with standard interferon and ribavirin therapy. These newer agents represent the most effective treatments available for the initial therapy of patients with chronic hepatitis C. A review of the clinical trials to date suggests certain similarities and differences between the two preparations. For both regimens, however, it is apparent that information concerning the predictability of response and the importance of adherence to the treatment regimens will be of great value in the therapeutic management of chronic hepatitis C. Although viral load and genotype, gender, age, and absence of fibrosis have been shown consistently to be important predictors of response, identification of additional host immune and genetic factors involved in determining outcome of antiviral therapy are necessary.