Meeting physical activity, sleep and sedentary behavior guidelines is associated with better cardiometabolic health and adiposity outcomes among children and youth. Unfortunately, recent estimates suggest that only 25.4% of adolescents in the US meet sleep guidelines, 26.1% meet physical activity guidelines, and only 5% meet guidelines for sleep, physical activity and sedentary behavior. Although some evidence indicates that there is a positive association between physical activity levels and sleep duration, findings among children and adolescents are not consistent and are limited by a predominantly cross-sectional study design. Although low income and minority youth are at a higher risk of not meeting both sleep and physical activity recommendations, it is unclear whether the sleep and physical activity relationship varies by racial, ethnic or socioeconomic group. Furthermore, exercise intensity appears to have a strong, positive relationship with sleep, although more research is needed to determine whether exercise at a light or moderate intensities can lead to improvements in sleep outcomes. This study aims to examine the association between physical activity and sedentary behavior, measured objectively at 11, 13 and 15 years of age, with subjectively-measured sleep at age 15. Furthermore, this study aims to understand whether the sleep and physical activity relationship varies by demographic characteristics and measures of adiposity.