To make this type of economic evidence more useful as part of the preschool policy debate, I set three goals: first, to identify the key challenges in measuring the economic returns from preschool programs; second, to summarize the range of estimates available from various benefit-cost analyses and some of the methodological differences that can account for the differences among them; and third, to explore the implications of the research on preschool-program impacts and economic returns, both for future research and for using benefit-cost analysis results to make policy decisions. (author abstract)