For more than a decade, researchers, and increasingly the public, have focused on childhood overweight as a personal and public health problem. As the number of children who are overweight has continued to grow, consensus has emerged that schools, as the places where children spend much of their time, have a critical role to play in reversing this trend. But while some promising programs, policies, and practices have been identified, there has been little attention to what front-line, building-based health professionals, specifically school nurses and the staffs of school-based health centers, can contribute to school-based interventions. This paper discusses what school health professionals and other stakeholders can do to prevent childhood obesity. InFocus: Body Mass Index for Children is appended.