We examined the affective correlates of aggression in children referred to a partial hospitalization program for the treatment of behavior disorders who did not have a mood or anxiety disorder. Parent and teacher ratings of the children's impulsivity, internalizing symptoms, affective reactivity, and aggression were examined for their interrelationships and then entered into regression analyses to predict the child's level of aggression in the home, at school, and in the treatment program. Intercorrelations among three affective reactivity factors were modest. Both internalizing symptoms and affective reactivity contributed to aggression severity beyond impulsivity and demographics. Only child irritability predicted treatment program aggression. Because of their potential role in understanding children's behavioral disturbances, internalizing symptoms and negative emotionality merit careful assessment and treatment in treatment programs serving hard-to-manage children with behavior disorders.