Connections between adolescents' social information processing (SIP), moral reasoning, and emotion attributions and their reactive and proactive aggressive tendencies were assessed. One hundred mostly African American and Latino 13- to 18-year-olds from a low-socioeconomic-status (SES) urban community and their high school teachers participated. Reactive aggression was uniquely related to expected ease in enacting aggression, lower verbal abilities, and hostile attributional biases, and most of these connections were mediated by adolescents' attention problems. In contrast, proactive aggression was uniquely related to higher verbal abilities and expectations of more positive emotional and material outcomes resulting from aggression. Discussion focused on the utility of assessing both moral and SIP-related cognitions, and on the potential influence of low-SES, high-risk environments on these findings.