This is a longitudinal study combined with cross-sectional studies of ADDH boys, normal boys, ADDH girls, and normal girls. Longitudinally, we will study three groups of boys, two with childhood ADDH disorders (ADDH-CD and ADDH-NCD) and normal control boys. Cross-sectionally, we will study 1) ADDH and normal six- year-old girls and 2) ADDH and normal eight-year-old boys. Full- field topography and a standardized electrode montage (International 10-20 system) will be used. We will compare the ERP patterns from two different modalities. We will study the effect of age on ERP and EEG measures. We will also study the effect of attention on ERP measures (Nd, P3) as a function of age, and we will study the effect of stimulant drugs on ERP and EEG measures in ADDH children as a function of age. Adult ERP and EEG data obtained from delinquent and nondelinquent adults who were formerly ADDH children will be available for comparison with our childhood data. The childhood ADDH syndrome is an important public health problem due to its prevalence, the lack of evidence that treatment in childhood affects long-term outcome, and the resulting (mainly untreatable) adolescent and adult psychopathological conditions, such as Conduct Disorder, Antisocial Personality Disorder, delinquency, and adult criminality.