The most common co-infection associated with HIV infection is viral hepatitis C. More than half of HIV-infected patients is coinfected with HCV in Russia. Both infections can have a reciprocal negative effect, what is reflected in an increase in the morbidity and mortality of co-infected patients compared with mono-infected patients. The negative role of HIV infection in the development of hepatitis C is manifested by the acceleration of the process of fibrosis and the formation of cirrhosis of the liver, as well as the frequent occurrence of hepatocellular carcinoma. The effects of HCV infection on the course of HIV infection have been less studied. It is known that hepatitis can slow down the immune reconstitution while receiving antiretroviral therapy. In addition, a violation of the hepatic barrier for products supplying from the intestine, apparently, can lead to additional activation of the immune system, aggravatted immunodeficiency, increased systemic inflammation and the development of AIDS-non-associated diseases, primarily cardiovascular diseases. Most researchers see the solution of the problem in the early start of antiretroviral therapy, as well as in the transition from interferon therapy to the appointment of drugs of direct action in the treatment of HCV infection.