This paper provides new estimates of the medium- and long-term impacts of Head Start on health and behavioral problems. We identify these impacts using discontinuities in the probability of participation induced by program eligibility rules. Our strategy allows us to identify the effect of Head Start for the individuals in the neighborhoods of multiple discontinuities. Participation in the program reduces the incidence of behavioral problems, health problems, and obesity of male children at ages 12 and 13. It lowers depression and obesity among adolescents, and it reduces engagement in criminal activities and idleness for young adults. (author abstract)