Food insecurity is experienced by millions of Americans and has increased dramatically in recent years. Due to its prevalence and many demonstrated negative health consequences, food insecurity is one of the most important nutrition-related public health issues in the U.S. In this article, we address three questions where economic insights and models have made important contributions: What are the determinants of food insecurity?; What are the causal effects of food insecurity on health outcomes?; and What is the impact of food assistance programs on food insecurity? We conclude with a discussion of the policy implications of the answers to these questions and future research opportunities in this research venue. Copyright 2011, Oxford University Press.