Pediatric obesity is considered a major public health problem in the United States today. Because excess body fat is associated with various health risks, clinicians and researchers have been investigating effective ways to reduce the incidence of pediatric obesity. To identify at-risk individuals, the U.S. health care community encourages the use of Body Mass Index (BMI),defined as weight/height2 (kg/m2),to classify children and adolescents into different health risk categories, including overweight and obese. However, the scientific validity of using BMI in pediatric population is questionable, even though BMI may be desirable as a means of tracking the growth patterns of individual children and adolescents in order to identify potential health problems. This review notes that BMI is not a reliable indicator of body fat for individual children and adolescents because it does not distinguish percent body fat from percent lean body mass. Neither does a single BMI value show the growth pattern of an individual child or adolescent. BMI does not account for distribution of body fat, ethnicity, and stages of maturation. Labeling children and adolescents as overweight or obese may lead to problems such as restrictive feeding by parents and unhealthy or unnecessary weight-control practices.