This study examined physiological and social-cognitive correlates of aggression in an in vivo laboratory provocation situation. Fifty-one male participants (ages 9 to 13) were selected based on teacher aggression screenings, ranging from normative to high levels. A provocation was induced by the experimenter communicating a threat from an unseen "peer" in the laboratory. Bivariate linear regression analyses showed that aggression significantly predicted heart rate at both pre- and postinduction, and aggression significantly predicted attributions of intent following the provocation. Results indicated that aggression was a significant predictor of changes in hostile attribution and heart rate following the threat induction. A positive correlation also was found between heart rate change and attribution change. The findings suggest that both physiological and social-cognitive processes should be addressed in clinical interventions with aggressive children.