Objectives: To assess associations of physical activity, diet, and sedentary behaviors with overweight and obesity. Methods: Analyses of the NHANES 2003-06 were conducted among 2368 US adolescents, ages 12-19. Self-reported diet and sedentary behavior measures were used; physical activity was assessed using accelerometers. Results: Television/video viewing (O R= 1.84; CI = 1.24, 2.69), physical activity (OR = 0.75; CI = 0.59, 0.95), and fiber intake (OR = 0.96; CI = 0.92, 0.99) were associated with obesity whereas television/video viewing was a risk factor for overweight (O R= 1.57; CI = 1.1, 2.63). Conclusions: Findings using accelerometer-measured physical activity are consistent with results from other studies using self-reported measurements. No interactions with ethnicity and gender were found.