Aim. To study the duration of the natural course of HIV infection and to identify its influencing factors. Subjects and methods. 938 outpatient case histories of adult HIV-positive patients registered at the dispensary and the data of 3403 AIDS patients registered in the computer base, including those on 2588 dead people, were retrospectively analyzed. Kaplan-Meier survival analysis and Cox regression model were used. Gender, age, and route of infection were regarded as potential factors influencing the natural course of HIV infection. Results. In Russia before the mass use of antiretroviral therapy (ART), the median survival from infection to death in the HIV-infected was 11.8 years; that from infection to establishment of AIDS was 11.6 years; the life expectancy following its diagnosis was 1.9 months. Patient age was a main factor influencing the course of HIV infection: in persons who had been infected with HIV at an age of over 35 years, lower CD4 lymphocyte counts and clinical progression occurred more rapidly than in those infected at a younger age. Less than 50% of the patients needed ART 5 years after HIV infection. Conclusion. An HIV-infected patient without ART survives almost twice less. It is necessary to detect HIV infection as early as possible and to regularly follow up patients regardless of the duration of infection in order to timely initiate its treatment.