The purpose of this project is: 1) to locate a population of adult psychiatric inpatients who exhibit signs and symptoms consistent with current concepts of childhood and adult Attentional Deficit Disorder (ADD), formerly labeled Minimal Brain Dysfunction (MBD), such as deficits in attention, arousal, and learning, emotional lability, impulsivity, hyperactivity, and immaturity involving control of activity, emotions and behavior; to assess the effects of treatment by methylphenidate on these patients; 2) to compare these effects with the effects on an adult population of psychiatric inpatients not considered to have ADD and 3) to determine if the use of psychostimulants with and adult ADD population can be a reasonable form of treatment. We will define the nature of this population using a variety of different measures: childhood and adulthood ADD screening forms, psychiatric rating scales, psychological tests, neurological and physiological assessments of sensory-integration, cerebral lateralization, neurogical softsigns, memory, learning, concentration, arousal, evoked potentials, skin conductance, activity, serum neurohormones, and urinary 3-methoxy-4-hydroxyphenylglycol (MHPG). Because we are interested in patients' responsiveness to treatment, we will also assess the quality of each subject's interpersonal interactions and assessments of mood. Subjects who appear to have a clinically positive response to methylphenidate will be asked to participate in a 12 month longitudinal study to examine the efficacy of treatment.