Klinefelter syndrome (KS) (47,XXY) is the most common sex chromosomal anomaly in males with a prevalence of 1 in 650 males. This clinically relevant condition represents 3%-4% of the total patient population in male reproductive medicine practices. Klinefelter syndrome can manifest in different physical, cognitive, and behavioral phenotypes. The classical phenotypic descriptions are gynecomastia, hypotonia, tall stature, and hypogonadism. Currently there is no known treatment plan for adolescents who are diagnosed with this genetic condition. However, it has been hypothesized that early intervention through androgen replacement therapy can emulate a normal progression of puberty and improve the academic, social, and behavioral aspects of these adolescents. Using standardized instruments, in the form of the Children Behavior Checklist (CBCL) and the Youth Self Report (YSR), we captured data on the patient’s competence and behavior, as well as the parents’ views on their child’s competence and behavior. These data were converted into percentile scores, T scores, and categorical data (normal, intermediate, and clinical). Difference of means was used to test for statistically significant differences between the scores of the KS patients and their parents on competence and behavioral aspects. T test for equality of means was run to determine if there was a significant difference between group scores. Pearson correlation tests were done to see if there was an association between demographics of patients and competence/behavioral scores. We believed that there would be no statistically significant difference between how the parents score their child in the CBCL and how the child scores himself in the YSR in terms of demographics. We also believed that there would be no statistically significant difference or correlation between demographics and individual competence/behavioral scores. A total of 39 groups of surveys were collected, together with demographic information on the maternal and paternal ages when the child was born, patient age, patient age when starting testosterone, patient age when starting anastrazole, and patient height and weight. We examined concordance frequencies in specific areas of the competence and behavioral questionnaires. Concordance was when the parent and the child agreed and evaluated the child as normal, intermediate, or clinical. Discordance was when the parents and the child disagreed; for example, the parent evaluated the child as “clinical,” but the child evaluated himself as “normal.” This study, to our knowledge, is the first chart review study that involves a wide age range of males with KS. The study extends previous findings by providing data on how early hormonal intervention can improve the outlook of these patients’ lives. When taking aromatase inhibitors, the KS adolescents showed an overall reduction of aggression and rule-breaking behavior. When taking testosterone at an earlier age, the patient was less likely to have withdrawal depression. We also found the most discordance in total competence scores, suggesting that some parents may have unrealistic academic expectations for their child. Thus, when examining the data, we had to be aware that there were varying views of success, which can shape how parents and child answer their respective surveys. Our findings demonstrate the significance of early detection and treatment of Klinefelter syndrome, a disorder that is severely under-diagnosed throughout the world. The results also show that the desire of parents for their KS child to do well in school may affect their opinions on how their child is actually performing. Some limitations to this study include the decision to receive early hormonal intervention that was made exclusively between parents and their urologist. Furthermore, the socioeconomic status (SES) and educational characteristics of the families were not properly controlled, although the patient population was mostly likely similar because of the location of the clinic. Future Klinefelter syndrome studies will need to focus on identifying the factors that contribute to the variability of behavioral symptoms. In turn, these studies will support the continuing development of evidence-based treatments for adolescents with Klinefelter syndrome.