Overweight among children has increased rapidly over the past two decades. According to growth charts of the Center for Disease Control, the average weight gain of children throughout the United States now exceeds the desirable norm. The trend has raised concerns about children’s diets and physical activity. A prevalent belief is that characteristics of the local food supply, such as the affordability of fresh produce and the density of food markets and restaurants, are associated with children’s diet and weight gain. However, there has been little empirical evidence. This study investigates these issues and finds an association between the relative cost of fruits and vegetables and excessive weight gain by elementary-age children.