 Walking to school is associated with higher levels of physical activity, which is an objective of Healthy People 2010. However, parents concerns about safety have been identified as a barrier that prevents their children from walking to school. A walking school bus WSB addresses these concerns by providing a supervised period of physical activity on the way to school. A WSB is a group of children led to and from school by responsible adults who walk together along a set route. The peer-reviewed literature on active travel to school is sparse. We evaluated a WSB program, to test the hypothesis that it would increase the proportion of children walking and decrease the proportion of children driven by car to school. 