Screening assessment: The screening visit(s) is/are used to determine if a child is eligible for participation. The child's teacher/daycare provider (with the parent's permission) and the parent(s) will need to complete some forms describing the child's problems with overactivity, impulsivity and inattention. The screening assessments may be completed over 1-2 visits. Each visit will take about 3-5 hours to complete. The research staff will evaluate each child to see if s/he has ADHD. Parents will be interviewed about their child's behavior. The child's teacher will be given several rating forms to complete. Parents will be asked to complete some questions about their child's development. Both parents (if available) and will be interviewed about their family histories.