There is evidence for a genetic contribution to attention-deficit hyperactivity disorder (ADHD), although no candidate genes have attained genome-wide significance to date. Given that the noradrenergic system has been implicated in ADHD, the gene for the α2-adrenergic receptor (ADRA2A) has been hypothesized to contribute to the pathogenesis of ADHD. The present investigation reports results from a meta-analysis of family-based studies that did not find a significant association between the MspI polymorphism of the ADRA2A gene and ADHD.