Abstract An attention deficit disorder with hyperactivity in children (ADDH) is now recognized in most countries although diagnostic practices differ. Evidence is presented to show that the two cardinal symptoms of poor attentional performance and high motor activity may be functionally and causally separate. Both are temporarily relieved in a proportion of subjects that respond to psychostimulants. Beneficial treatment decreases noradrenergic metabolism and normalizes variable levels of dopaminergic metabolism. Parallels are drawn with other clinical syndromes arising from changed catecholaminergic activity and with behavioral interpretations of the result of damage to the dorsal noradrenergic bundle and dopaminergic A10 nucleus. Prognosis of ADDH subjects after treatment remains poor. There may be a further defect of neurotransmitter metabolism in the ADDH syndrome. Research strategies are suggested based on the neurobiological correlates of the cognitive style of ADDH subjects and septal function in the animal model of the hypertensive rat.