The acute inflammation of liver in patients (acute hepatitis) can be produced by different chemicals (such as alcohol, drugs) and different viruses (such as A, B, C, D, E, F, G). The hepatitis C virus (HCV) was discovered in 1989, which is dominantly transmitted via of blood transfusion or of intravenous medicine. The etiological role of HCV has gradually increased in Hungary and in the World, which produces acute (hepatitis) and chronic (hepatitis, liver cirrhosis, hepatocellualr carcinoma) liver diseases. The lymphocyte-mediated immunological mechanisms have a key-role in the developement of different forms of viruse-induced liver diseases. The lymphocytes together hepatogenic (due to liver diseases) and lymphogenic (due to non-Hodgkin lymphoma) actions, consequently the lymphocytes-mediated mechanisms are involved in the developement of malignant diseases of liver and lymphoid tissues. This monograph details the results of our studies due to the mechanisms of HCV-induced developement of non-Hodgkin lymphoma in patients. This monograph is offered for molecular biologists, virologists, genetics, internists, pathologists, experimental and clinical hepatologists.