We anticipate the establishment of clinical, neuropsychological, and genetic database of 300 ADHD families (200 in NSC96-2628-B-002-069-MY3 and 100 in this project), completion of the screening of several candidate genes, and identification of potential genetic variants for ADHD, and determination of their association with ADHD diagnosis and symptoms and its endophenotype in a Taiwanese sample. The long-term objectives are to identify the behavioral phenotypes and endophenotypes that are close to the biological expression of genes underlying ADHD. The findings of different approaches to identify the genetic etiologies for ADHD in this pilot study should help us to determine the most promising approach for future molecular genetic and pharmacogenetic study on ADHD.