Objectives: To assess weight-related concerns and behaviors in a population-based sample of adolescents and to compare these concerns and behaviors across sex and weight status. Design: The study population included 4746 adolescents from St Paul or Minneapolis, Minn, public schools who completed surveys and anthropometric measurements as part of Project EAT (Eating Among Teens), a population-based study focusing on eating patterns and weight concerns among teenagers. Main Outcome Measures: Measured weight status, weight-related concerns (perceived weight status, weight disparity, body satisfaction, and care about controlling weight), and weight-related behaviors (general and specific weight control behaviors and binge eating). Results: Weight-related concerns and behaviors were prevalent among the study population. Although adolescents were most likely to report healthy weight control behaviors (adolescent girls, 85%; and adolescent boys, 70%), also prevalent were weight control behaviors considered to be unhealthy (adolescent girls, 57%; and adolescent boys, 33%) or extreme (adolescent girls, 12%; and adolescent boys, 5%). Most overweight youth perceived themselves as overweight and reported the use of healthy weight control behaviors during the past year. However, the use of unhealthy and extreme weight control behaviors and binge eating were alarmingly high among overweight youth, particularly adolescent girls. Extreme weight control practices (taking diet pills, laxatives, or diuretics or vomiting) were reported by 18% of very overweight adolescent girls, compared with 6% of very overweight adolescent boys (body mass index, ≥95th percentile). Conclusion: Prevention interventions that address the broad spectrum of weight-related disorders, enhance skill development for behavioral change, and provide support for dealing with potentially harmful social norms are warranted in light of the high prevalence and co-occurrence of obesity and unhealthy weight-related behaviors.