The ultimate goal of this study is to find specific polymorphism of candidate genes associated with endophenotypes and/or phenomenological phenotypes of ADHD. We propose to replicate the analysis of the candidate genes identified by previous genetic studies on ADHD using the candidate gene association study design (family-based case control study using parental controls) to validate the findings from other research groups. These results will lead our team: (1) to resolve controversies over inconsistent findings in previous genetic studies and contribute to the literature on the validity of ASD using clinical and genetic data; (2) to study the pathogenetic process of abnormal genes in abnormal neuropsychological and neurobiological functions of ADHD; (3) to delineate the nature and the effect of gene-gene interaction in the etiology of ADHD.