"Head Start is a comprehensive, early childhood development program designed to augment the human capital and health capital levels of disadvantaged children. Evaluations of Head Start have tended to focus on cognitive outcomes; however, there is increasing recognition that other important outcomes can be influenced by participation. This article evaluates the long-term impact of Head Start participation on smoking behavior in young adulthood by comparing the behavior of adults who attended Head Start with those of siblings who did not. We find that participation in Head Start reduces the probability that an individual smokes cigarettes as a young adult." ("JEL" I12, I28, I38) Copyright (c) 2009 Western Economic Association International.