Baseline data from 640 injection drug users in the Stop AIDS for Everyone study, an HIV preventive intervention were used to examine gender differences in self-reports of injection behaviors. In both the bivariate and multivariate analyses men reported injecting alone, in semipublic areas, and at their mother's residence more often than women. In the bivariate analyses, women reported denser personal networks, and in the multivariate analyses, women reported significantly greater overlap between their drug and sex networks. These data suggest that this overlap of sex and drug networks may reduce women drug injectors' ability to adopt and maintain HIV protective behaviors. The data also suggest that interventions need to address gender differences in the social context of risk behaviors.