This discussion summarizes some of the key conceptual and methodological contributions of the four articles in this special section on social information processing (SIP) and aggression. One major contribution involves the new methodological tools these studies provide for future researchers. Eye-tracking and mood induction techniques will make it possible for SIP researchers to study attentional and emotion-related processes across the six SIP steps. In addition, the STEP-P instrument will open up the study of emotionally-charged aspects of preschoolers' early SIP. A second contribution is how these articles emphasize the dynamic interplay of emotional and cognitive processes in the emergence of children's and adolescents' aggressive tendencies. Finally, implicit developmental themes are raised by several of these studies. Discussion concludes with suggestions for future research, including a focus on the positive (i.e., non-disruptive) role of emotions, and on the connections between moral development and aggression.