Walking to school is a promising form of physical activity that has the potential to make population-level changes to improve childhood obesity in the US. A walking school bus (WSB) is a group of children who walk to and from school chaperoned by responsible adults, usually parents. Despite the growing popularity of walk to school programs in the US, long-term controlled studies are lacking. The authors sought to help fill this gap by conducting a pilot assessment of the effect of a WSB program in a low-income community in Seattle, Washington.