A new generation of Americans, raised in immigrant families, has been coming of age. They are transforming their adoptive society even as they themselves are being transformed into the newest Americans. Over time, these children will decisively shape the character of their ethnic communities and, indeed, the nation as a whole. The long-term effects of contemporary immigration will hinge more on the trajectories of these youths than on the fate of their parents. These children of today’s immigrants - a post-immigrant generation oriented not to their parents’ immigrant pasts but to their own American futures - are here to stay, and they represent the most consequential and lasting legacy of the new immigration to the United States. This paper examines three key issues: language acquisition; ethnic “identities”; and academic achievement and career ambition. It relies on the latest results of the Children of Immigrants Longitudinal Study (CILS), an investigation of the educational performance and social, cultural and psychological adaptation of children of immigrants, the largest study of its kind and the only longitudinal study of the new generation. The study has followed the progress of a sample of teenage youths representing 77 nationalities in two key areas of immigrant settlement in the United States: Southern California and South Florida. The results have clear implications for the future of these youths and for public policy responses.