Access to food is essential to optimal development and function in children and adults. Food security, food insecurity, and hunger have been defined and a U.S. Food Security Scale was developed and is administered annually by the Census Bureau in its Current Population Survey. The eight child-referenced items now make up a Children's Food Security Scale. This review summarizes the data on household and children's food insecurity and its relationship with children's health and development and with mothers' depressive symptoms. It is demonstrable that food insecurity is a prevalent risk to the growth, health, cognitive, and behavioral potential of America's poor and near-poor children. Infants and toddlers in particular are at risk from food insecurity even at the lowest levels of severity, and the data indicate an "invisible epidemic" of a serious condition. Food insecurity is readily measured and rapidly remediable through policy changes, which a country like the United States, unlike many others, is fully capable of implementing. The food and distribution resources exist; the only constraint is political will.