The results of the development and realization principles of the project on the decrease of harm, envisaging work in three directions (the determination of the technology of using drugs, the exchange of syringes/needles and other accessories, as well as laboratory examination for the presence of antibodies to HIV, hepatitis B and hepatitis C viruses and consultations of narcologists). 1075 injecting drug users took part in this project. Out of 611 participants filling-in the questionnaires, 338 persons underwent tests for HIV and 3 of them were found to be HIV-infected; out of 305 persons screened for the presence of markers of hepatitis B virus, positive results were obtained in 98 (32% of cases); in 218 (65%) out of 335 persons antibodies to hepatitis C virus were found (49 persons, i.e. 14%, had hepatitis C registered in the medical history and in the rest antibodies were detected for the first time). The preventive program of the decrease of harm was assessed as effective.