The past decade has brought important new advances in the fields of genetics, behavioral genetics, linguistics, language acquisition, studies of language impairment, and brain imaging. Although these advances are each highly relevant to the determination of what a child is innately prepared to bring to language acquisition, the contributing fields of endeavor have traditionally been relatively self-contained, with little cross communication. This volume was developed with the belief that there is considerable value to be gained in the creation of a shared platform for a dialogue across the disciplines. Leading experts in genetics, linguistics, language acquisition, language impairment, and brain imaging are brought together for the purpose of exploring the current evidence, theoretical issues, and research challenges in a way that bridges disciplinary boundaries and points toward future developments in the search for the genetic and environmental bases of language acquisition and impairments. This collection provides discussions and summaries of: *breakthrough findings of the genetic underpinnings of dyslexia; *theoretical and empirical developments in the specification of a phenotype of language acquisition and impairment; *evidence of familiarity and twin concordances of specific language impairment; and *new evidence from brain imaging. It concludes with a critical response from an advocate of rational empiricism.