IN THIS issue of the ARCHIVES, Lonczak et al1 present data from the long-term follow-up of a multilevel youth development intervention, the Seattle Social Development Project (SSDP). The article documents the longitudinal effects of an elementary school–based intervention on sexual behavior, pregnancy, birth, and the acquisition of sexually transmitted diseases (STDs) at age 21 years. Earlier reports on this same program demonstrated its measurable beneficial effects on violent and nonviolent crime, substance use, sexual activity, pregnancy, school achievement, grade repetition, dropping out of school, suspension and expulsion, and delinquency.2- 3 The current findings add to the earlier longitudinal follow-up and have significant research and policy implications for STDs and pregnancy prevention interventions with children and adolescents. First, the results of this program's broad focus on youth development provide evidence that strengthening social and psychological skills, rather than targeting specific risk behaviors, can protect against an array of health risks, including STDs, human immunodeficiency virus infection, and pregnancy in adolescents and young adults. Second, this study shows that early intervention can have an enduring impact as children grow and develop into young adults. Third, this report provides initial evidence that multilevel interventions can yield a synergistic and sustained impact throughout a lengthy follow-up period.