An analysis of risk factors emerging in IDU's surroundings, their influence on models of drug using and HIV spreading and probable HIV prophylactic opportunities are presented in the article. Qualitative description of micro-environment of drug using, existing social networks of IDUs and practices of drug using in Barnaul are also presented here. As a result of the given research a specifics of influence of micro-environment (social network) influence on practices of injected drugs using. It is closely connected as with a starting of a narcotic career (situation of accustoming to a drug using) as with the practices of join using of injecting instruments.