From an applied behavior-analytic perspective, aggression in people with intellectual disabilities is mostly maintained by social reinforcement consequences. However, nonsocial consequences have also been identified in functional assessments on aggression. Behaviors producing their own reinforcement have been labeled "automatic" or "nonsocial" in the behavior-analytic literature, a label that bares a striking resemblance to biobehavioral explanations of reward-seeking behaviors. Biobehavioral studies have revealed that aggression activates the same endogenous brain mechanisms as primary reinforcers like food. Therefore, integrating brain-environment explanations would result in a better understanding of the functional mechanisms associated with nonsocial aggression. The purpose of this paper was to explore aggression as a reinforcing consequence for reinforcement-seeking behaviors in people with intellectual disabilities. First, the literature establishing aggression as reinforcement for arbitrary responding will be reviewed. Next, the reward-related biological process associated with aggression was described. Finally, the paper discusses what might be done to assess and treat aggression maintained by nonsocial reinforcement.