Within the framework of puberty and maturation, the study: 1) described longitudinal patterns of physical activity; 2) assessed longitudinal changes in physical activity and concomitant changes in blood pressure and body fatness; and 3) determined psychosocial predictors of changes in physical activity. The investigators hypothesized that there would be a monotonic decrease in physical activity and that psychosocial variables would predict changes in physical activity. The study population consisted of 189 sixth grade, mostly African-American, girls in Fort Bend Independent School District, Missouri City, Texas. The girls were measured for four and a half years, ages 11 or 12 at entry of the study. Anthropometry, sexual maturation, blood pressure, physical activity habits and psychosocial predictors were measured twice a year for a total of nine examinations. Data on dietary, smoking and drinking habits were collected annually. Activity patterns, psychosocial predictors and other habits were assessed by interviews and questionnaires. Sexual maturation was assessed by menarche and the Tanner stages. Skinfold and circumference measures determined body fatness and body fat distribution.