Tested the hypothesis that aggressive boys' tendency to attribute hostile intentions to peers is exacerbated in a negative emotional state. Twenty-nine highly aggressive boys in special education, 12 moderately aggressive boys in regular education, and 16 nonaggressive boys in regular education inferred peers' intentions in 8 vignettes concerning ambiguous provocation by peers. Mild negative emotions were induced by unjust loss of a manipulated computer game. Half the vignettes were completed in this negative emotional state. After completion of all vignettes, the game was played again and won to reinduce positive feelings. Self-ratings of feelings obtained throughout the study showed the manipulations consecutively induced negative and positive feelings. Negative feelings increased hostile attribution of intent in the highly aggressive group. Highly and moderately aggressive boys responded more aggressively than nonaggressive boys.