Objective and reliable techniques for the assessment of attention deficit disorders (ADD) with and without hyperactivity in children have remained largely unavailable to psychologists, educators and pediatricians. As a consequence, they have tended to base their evaluations of ADD solely on observations and teacher reports, or on measures such as the Wechsler scales, which have been shown to discriminate poorly between groups of hyperactive and nonhyperactive children. A behavioral measure of ADD, called the Gordon Diagnostic System (GDS), has shown considerable promise as a precise, valid and efficient technique for the diagnosis of attention disorders. The GDS contains two measures: the Delay Task, which measures the ability to inhibit responding; and the Vigilance Task, which assesses sustained attention. Research studies have shown that these game-like tasks differentiate accurately between hyperactive and non-hyperactive children. Normative data on GDS performance have been established based on a study of 220 nonhyperactive boys and girls from 6 through 11 years of age. Information on test-retest reliability is also available. (Author)