Schools have the potential to make valuable contributions to both the prevention and treatment of childhood obesity. This article reviews the research on school-based interventions to prevent and treat obesity. A literature search from 1965 to the present on school-based treatment of obesity, identified 11 controlled experimental studies. The results show positive, though modest short-term results. Relatively few primary prevention research studies, targeted specifically to preventing obesity, have been conducted. Therefore, efficacy has not been established. Both primary and secondary obesity interventions have a role in schools. A comprehensive, integrated model for school-based obesity prevention is presented. This model, building upon the comprehensive school health program model, consists of eight interacting components: health instruction; health services; school environment; food service; school-site health promotion for faculty and staff; social support services; physical education classes; and integrated and linked family and community health promotion efforts. While multi-faceted community-wide efforts are needed to address the growing problem of obesity, schools are in a unique position to play a pivotal role in promoting healthy lifestyles and helping to prevent obesity.