African American adolescent girls are at an increased risk of being inactive and overweight.  Aspects of the internal and external environments of urban middle schools, both built and perceived, may be contributing factors for inactivity and obesity in low-income, African American adolescent girls.  The purpose of this study is to evaluate both the perceived and objectively measured internal and external physical activity environment of urban middle schools serving predominantly low-income African American students in Baltimore, MD, and to examine how these influences affect the body composition and physical activity of low-income, African American adolescent girls in urban public middle schools.  Individual evaluations, including body composition, physical activity, and perceived internal and external school physical activity environment, will be conducted.  Objective measures will be taken of the school physical activity environment.