Theories of aggressive behavior and ethological observations in animals and children suggest the existence of distinct forms of reactive (hostile) and proactive (instrumental) aggression. Toward the validation of this distinction, groups of reactive aggressive, proactive aggressive, and nonaggressive children were identified (n = 624 9-12-year-olds). Social information-processing patterns were assessed in these groups by presenting hypothetical vignettes to subjects. 3 hypotheses were tested: (1) only the reactive-aggressive children would demonstrate hostile biases in their attributions of peers' intentions in provocation situations (because such biases are known to lead to reactive anger); (2) only proactive-aggressive children would evaluate aggression and its consequences in relatively positive ways (because proactive aggression is motivated by its expected external outcomes); and (3) proactive-aggressive children would select instrumental social goals rather than relational goals more often than nonaggressive children. All 3 hypotheses were at least partially supported.