The proposed etiologies, clinical features, prognosis, and drug therapy of attention deficit disorder (ADD) are reviewed. Attention deficit disorder is a common neurobehavioral problem in children that manifests as hyperactivity, impulsivity, and inattention. It may persist into adolescence and adulthood and predispose the patient to antisocial and substance-abuse disorders. Stimulant agents are the drugs of first choice for pharmacologic treatment of ADD. Methylphenidate is the most frequently used stimulant because of its reduced potential for abuse and less troublesome adverse effects compared with dextroamphetamine. Stimulant medications are usually well tolerated, with nervousness and insomnia being the most common adverse effects. The potential for stimulant-induced growth suppression during long-term treatment should be dealt with prospectively by providing drug holidays. Tricyclic antidepressants and monoamine oxidase inhibitors may be used in patients who do not respond adequately to stimulant agents. Low doses of the antipsychotic agents haloperidol, chlorpromazine, or thioridazine may be used as adjunctive treatment for ADD symptoms of hyperactivity and aggressiveness. Attention deficit disorder is not a benign disorder that children necessarily outgrow. Pharmacologic therapy should be combined with nonpharmacologic therapy to provide the greatest long-term benefits.