2,516 US adolescents were followed for 5 years from 1999 through 2004. The data show continued and, in some cases, increasing socioeconomic disparities in risk for overweight. Youth from low-SES backgrounds are at increased risk for overweight and are more likely to remain overweight (boys) or become overweight (girls). Designing obesity prevention and treatment interventions that reach and address the unique needs of youth and families from less-advantaged socioeconomic backgrounds is a public health priority.