The kinetics of hepatitis C virus (HCV) RNA during the first weeks of interferon-based antiviral therapy can be analysed by specific mathematical models. Those models have been inspired by previous work on the kinetics of human immune deficiency virus (HIV) and hepatitis B virus (HBV) during antiviral therapy and are able to summarize important features of early response to antiviral therapy in patients chronically infected with HCV. Kinetic parameters of the underlying biological processes as viral clearance and infected cell loss as well as an efficiency factor of therapy on viral production can be obtained when fitting frequent quantifications of HCV RNA with such models. The main aims of analysing hepatitis C viral kinetics include the efficient comparison of different treatment regimens, prediction of virological response, and conclusions on antiviral mechanisms of therapy.