Attention deficit hyperactivity disorder is a prevalent disorder characterized by hyperactivity, impulsivity, and attentional dysfunction. It is familial and heritable. Its pathophysiology is thought to involve an abnormality of the brain's dopaminergic neurotransmitter system. Recent work has identified a distinct polymorphism of the dopamine D4 receptor gene in normal people with a behavioral temperament profile characterized by features of "novelty seeking" which include impulsive and exploratory behaviors. These personality traits are also characteristic of children with attention deficit hyperactivity disorder, especially the hyperactive-impulsive type. This study investigated the relationship between dopamine D4 receptor gene polymorphism, temperament categories, and attention deficit hyperactivity disorder in 81 children with the disorder and 24 control subjects. There was no significant association between dopamine D4 receptor gene alleles, Novelty Seeking traits, and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnosis of attention deficit hyperactivity disorder--Hyperactive impulsive type or Inattentive type.