• Four hundred college men were screened on a measure of vigilance, the Continuous Performance Test (CPT). The individuals with good and poor attention (the upper and lower 5% of the CPT score distribution) were compared on multiple measures of psychiatric disturbance, cognition, and psychophysiologic function. The attention dysfunction group (lower 5%) had a higher incidence of symptoms of hyperactivity both in childhood and as adults, but had no higher incidence of other psychopathology as assessed with either the Research Diagnostic Criteria or the Minnesota Multiphasic Personality Inventory. Cognitive differences between the lower and upper CPT groups, including differences on Wechsler Adult Intelligence Scale subtests, the Stroop test, reaction time, and evoked potentials, substantiated an attention dysfunction syndrome. Thus, attentional dysfunction in young adults seems more closely linked to hyperactivity than to current psychopathology.