A very common cause of children's behavior disorder disturbance is an entity described as the hyperkinetic impulse disorder. This is characterized by hyperactivity, short attention span and poor powers of concentration, irritability, impulsiveness, variability, and poor schoolwork. The existence of this complexity may lead to many psychological problems, due to the extremely irritating effect it has on parents and teachers. Often the history reveals some clear-cut organic insult to the central nervous system, before birth, during birth, or during the first 5 years of life, which presumably may result in dysfunction of the diencephalon. In many cases, however, though clinically they seem identical, the history shows no such factor. Such dysfunction of the diencephalon exposes the cortex to unusually intense storms of stimuli from peripheral receptors coming through the diencephalon and the reticular activating system and may interfere with the function of the cortex and its relationships with diencephalon. The photo-Metrazol determination done in children showing this syndrome is significantly different from those without the syndrome. This situation is in time overcome by the operation of normal maturational processes. Until such takes place, apparently amphetamines and possibly other medications have a very specific ameliorating effect on this syndrome by means of a direct action on the diencephalon. This suggestion is supported by the data given on the effect of amphetamine in raising the photo-Metrazol threshold in such children. This situation has many physiological and psychodynamic implications.