There has been a recent upswing in research concerning the prevention of aggression in youth. Much of this research makes a distinction between proactive and reactive aggression. Proactive aggression is intended to achieve an instrumental goal, while reactive aggression is an emotional response to provocation. However, much of the research on this distinction has been focused on children. Thus, little is known about this distinction among adolescents. As such, the goal of this study was threefold. The first goal was to explore if prosocial and aggressive subtypes could be identified from the self reports of adolescents. The second goal involved exploring the differences in aggressive and prosocial behavior, as well as normative acceptability beliefs, by age and gender. The third goal of the study was to examine associations among the aggressive and prosocial behavioral subtypes and their relations to normative beliefs about aggression. The authors administered a series of aggressive and prosocial behavior questionnaires to 250 students at 2 middle schools and 1 high school. The mean age of the participants was 14.6 years. Questionnaire instruments probed for two types of aggression (proactive and reactive) and three types of prosocial behavior (proactive, reactive, and altruistic). Participants also completed behavior rating scales and measures of their beliefs about aggression. Results of principal component analysis revealed three subtypes of aggressive and prosocial behavior: aggressive, prosocial, and proactive prosocial. Proactive prosocial behavior was significantly related to aggression and aggression supporting beliefs; however, other prosocial behavior was negatively correlated with aggression. These findings indicate that proactive prosocial behavior may be rooted in motivations and beliefs that are more similar to aggression than to prosocial behavior. As measured in this study, proactive prosocial behavior represents a manipulative, goal-directed form of prosocial behavior. It may be useful for researchers to integrate an awareness of proactive prosocial behavior into studies of youth and adolescent aggression. Future research should further probe distinctions in prosocial behavior with more diverse samples. Tables, references