Existing research demonstrates that peer relationships are an important part of children's social contexts, with different types of peer interactions related to different benefits and risks as children develop. However, little is known about how individual child behaviors contribute to peer interactions and how various types of peer interactions differ from one another. This study examines how third grade children's prosocial and aggressive behaviors predict the number of mutual friendships they possess, the relative amount of social acceptance and rejection they experience from peers, and their prominence within their classroom network. Additionally, this study differentiates peer interaction measures by assessing reciprocated friendships, sociometric ratings, and social network analyses of betweenness centrality and rank prestige. For this dissertation, the prosocial and aggressive behaviors of 204 children in 13 classrooms were assessed in the fall by three types of informants (teacher, peer, and self-report). These behavioral assessments were then used to predict children's peer relationships four months later. Using multiple regression analyses, this study finds that prosocial behaviors can beneficially affect the development of friendship, peer acceptance, and network centrality and reduce peer rejection. Supporting the notion that while they may not finish first, these findings suggests that nice guys do not finish last. Conversely, aggressive behaviors are found to often lead to negative peer outcomes such as peer rejection and friendlessness, especially when they occur without prosocial behavior. However, in combination with prosocial behavior, aggression increased network betweenness centrality, the likelihood of having a friend, and of being accepted by peers. The use of multiple informants in this study and their varying relationships with each outcome offer one explanation for why other studies have found aggression to be positively, negatively, and neutrally associated with peer interactions. Lastly, this study further supports the finding that friendship, peer preference, and network centrality are unique aspects of children's social lives. This dissertation is one more step towards understanding the complexity of prosocial and aggressive behaviors and the different aspects of peer interactions.