Objective To investigate association of the 48 bp variable number of tandem repeat (VNTR) polymorphism in the dopamine D 4 receptor gene (DRD4) exon Ⅲ with attention deficit hyperactivity disorder (ADHD) in Chinese children Methods A case control association study and a family based association study with Exact Transmission Disequilibrium Test (ETDT) were used to analyze the association of polymorphism in the dopamine D 4 receptor gene exon Ⅲ with ADHD 176 ADHD children diagnosed according to DSM...