Hepatitis C virus (HCV) is an extremely dangerous human pathogen. It is widespread all over the world and often leads to the development of chronic hepatitis C (CHC), which can eventually result in cirrhosis a hepatocellular carcinoma. The efficiency of the current applied methods of treatment of HCV infection remains unsatisfactory. The main course of development of CHC and of therapeutic problems is the genetic polymorphism of HCV. The conducted analysis of the structure of the virus' population permits are conclude that the degree of diversity it presents is a crucial agent in the prediction of the outcome of IFN and ribavirin therapy.