This study examined personal networks of adult male prisoners (N = 250) during a high-risk period prior to their incarceration. We present a descriptive portrait of network size, density, and relational type, and we then document the nature of ties within that network, focusing specifically on alters’ criminal involvement, criminal opportunity, and reinforcement of criminal behavior. We found that prisoners’ networks were large and dense, and that they were composed primarily of family and romantic partners. Most prisoners are not embedded in a personal network saturated with criminal influence before coming to prison. Yet, a small proportion are exposed to exceptionally negative influence, which, it is argued, may increase the risk of negative outcomes upon release if not addressed by evidence-based programs.