Project HeartBeat! was a longitudinal "growth" study of cardiovascular disease (CVD) risk factors and body composition in childhood and adolescence. Its findings demonstrate patterns of change from ages 8 to 18 years in anthropometric indicators of adiposity, blood lipid components, and blood pressure measurements, as well as the varying inter-relations among these patterns. Especially noteworthy are differences among associations between the two components of BMI (kg/m(2))-the lean or fat-free mass index, and the fat mass index-and each of several CVD risk factors. Policy development and public health recommendations for CVD prevention beginning in childhood have evolved over 30 years or more. A new impetus to action is the recognized increase in the prevalence of childhood overweight and obesity. Intervention to prevent obesity can have a major impact in preventing CVD risk factors more broadly. Opportunities to strengthen interventions for CVD prevention in childhood and adolescence include updated algorithms for monitoring body composition, blood lipids, and blood pressure throughout childhood and adolescence through use of the Project HeartBeat! study results.