The intervention to be tested in this study draws upon theoretical and empirical evidence suggesting that peer educator programs can have significant effects on the risk-related behaviors of both the educators and the peers whom they educate. Providing peer educator training to IDUs may efficiently cultivate sustainable protective behavioral norms related to injection and sexual risk among the IDU educators' social networks. Prior studies have demonstrated that peer educator programs can realize such normative changes, and it is hypothesized in this study that these normative changes will be reflected in significant reductions in the rates of HIV transmission among the peer educators and the members of their social networks.