Abstract: The progression to adult antisocial behavior is the least desirable developmental trajectory for children with ADHD. An unremitting pattern of physical aggression appears of great import when predicting long-term outcome. However, a profile characterized by behavioral and cognitive impulsivity and emotional lability may indicate a greater likelihood of the progression to adult antisocial behavior and violent impulse-control disorders. This constellation of behaviors appears to be, at least in part, mediated by brain serotonergic systems. The contribution of cognitive impairments, as manifested by executive function deficits, diminished moral reasoning, and impaired empathic ability, to the emergence and persistence of antisocial behavior has yet to be discerned.