Klinefelter Syndrome (KS) is a relatively common (1/500 to 1/1,000) genetic syndrome caused by an extra X chromosome in males, leading to an XXY karyotype. In most cases, the physical and neurobehavioral characteristics of KS are relatively mild, and KS is not usually associated with moderate or severe mental retardation. However, KS is often associated with significant language-based learning disabilities and executive dysfunction, making it a plausible genetic model for understanding the neurobiology of these areas of cognition that are so fundamental to learning in a classroom. Additionally, the psychosocial aspects of KS, which can have a significant impact on school performance and learning, have been explored only on an anecdotal level. We have conducted pilot studies in a small group of KS adolescents and adults to begin to identify the social, emotional, and adaptive behavior issues facing KS subjects and have identified several areas for further research. This includes characterization of mild maladaptive behaviors, as well as significant strengths in other areas. Further work is needed to determine how the social-emotional and cognitive features of the disorder interact or change over the lifetime of subjects and how the learning disabilities respond to hormonal or cognitive-based therapy.