Objective. With the increasing prevalence of pediatric obesity, it is important to identify high-risk populations of children to direct limited resources for prevention and treatment to those who are most vulnerable. The objectives of this study were to determine the prevalence of overweight in children who are clients of community health centers in medically underserved areas of the Health Resources and Service Administration regions II and III (Mid-Atlantic and Puerto Rico), compare this prevalence to nationally representative data, and contrast prevalence data between geographic areas and racial/ethnic groups. Methods. The charts from a representative sample of 2474 children using 30 community health centers in 2001 were abstracted to collect clinically measured weight and height. Overweight was defined as a body mass index of [greater than or equal to] 95th percentile of a reference population. To generate an unbiased estimate of overweight, multiple imputations were used for missing data. These data were compared with the 1999-2002 National Health and Nutrition Examination Survey. Results. The prevalence of overweight was elevated in this sample of children aged 2 to 5 years (21.8%; 95% confidence interval [CI]: 19.1-24.8) and 6 to 11 years (23.8%; 95% CI: 16.9-27.7) compared with the 1999-2002 National Health and Nutrition Examination Survey (10.3% and 15.8%, respectively). No significant differences in prevalence were observed between Asian American (18.2%; 95% CI: 11.2-28.3), Hispanic (24.6%; 95% CI: 21.3-28.2), non-Hispanic black (25.6%; 95% CI: 20.8-30.9), and non-Hispanic white (22.8%; 95% CI: 19.0-27.0) children. Furthermore, no differences in prevalence were observed between children using community health centers in continental urban (23.7%; 95% CI: 20.6-27.2), suburban (24.0%; 95% CI: 20.0-28.5), or rural (22.9%; 95% CI: 19.3-26.9) areas. Conclusions. The present study identified a population of children at particularly high risk for obesity based on the type of health care delivery system they use regardless of race/ethnicity or geographic characteristics. Because community health centers are experienced in prevention and serve >4.7 million children in the United States, they may be a particularly promising point of access and setting for pediatric obesity prevention. Pediatrics 2005;116:e381-e388. URL: www.pediatrics.org/cgi/ doi/10.1542/peds.2005-0104; African Americans, Asian Americans, child, community health centers, delivery of health care, European Continental Ancestry Group, Hispanic Americans, medically underserved area, obesity, primary health care, Puerto Rico, rural health, suburban health, urban health.