Following acute hepatitis C virus infection (HCV), a significant percentage of patients do not clear the virus and develop a chronic hepatitis C. The symptoms, when they exist, are usually unspecific. Besides, approximately one third of the patients present extrahepatic manifestations of the infection, basically due to the lymphotropism of HCV. Outstanding amongst these, due to their clear association with HCV, are mixed cryoglobulinaemia and the production of autoantibodies (autoAb). Other diseases such as non-Hodgkin lynphoma (NHL) or autoimmune thyroiditis do not have a clearly established association. Although the majority of patients with chronic hepatitis C have slight or moderately high levels and fluctuations of transaminases, as many as one third of those infected can show persistently normal levels of transaminases. The diagnosis of chronic HCV infection is based on serological tests, which detect the presence of antibodies against HCV, and on virological tests that detect RNA of the HCV, which confirm the existence of active infection. Finally, an important topic of chronic HCV infection, following diagnosis, is to ascertain the stage of fibrosis and the degree of inflammation, since both characteristics are very important for predicting the natural evolution and the need for treatment. Nowadays, this information can only be obtained through liver biopsy, which is recommended in patients with chronic HCV infection and high transaminases. Whether liver biopsy should be performed in patients with normal transaminases is still subject of controversy.