Social networking sites are increasingly popular among teenagers, with 25% of 200 million MySpace users estimated to be minors. Adolescents' Web profiles can place them at risk of a number of adverse consequences because of the health risk information displayed, such as sexual activity and substance use. In this study, Moreno and colleagues examined 500 profiles of self-reported 18-year-olds in the United States. More than half of the profiles referenced 1 or more high-risk behaviors: 24% sexual behaviors, 41% substance use, and 14% violence. Male adolescents were more likely to display references to violent behavior, while female adolescents were more likely to display references to sexual behaviors. Involvement with church or sports decreased the likelihood of references to health risk behaviors. It is important for both parents and pediatricians to be aware of these sites and to counsel adolescents on the dangers of displaying personal and inappropriate material on them. These sites may also serve as a venue for interventions in high-risk youth.