Purpose This article describes a database that was created in the process of conducting a large-scale epidemiologic study of specific language impairment (SLI). As such, this database will be referred to as the EpiSLI database. Children with SLI have unexpected and unexplained difficulties learning and using spoken language. Although there is no uniform standard for the diagnosis of SLI, the construct encompasses a language deficit occurring in the presence of grossly normal sensory and nonverbal cognitive abilities (H. Tager-Flusberg & J. Cooper, 1999). Although these language difficulties are most apparent during the preschool and early school years, evidence now exists that these problems are usually present well into adulthood and are probably present throughout a person’s life (see, for instance, C. J. Johnson et al., 1999; S. E. Stothard, M. J. Snowling, D. V. M. Bishop, B. B. Chipchase, & C. A. Kaplan, 1998; J. B. Tomblin, 2008).

Discussion Much of what we know of these children has come from research on children who have been clinically identified and served. Certainly, by studying those who are being served, our research base is most likely to be relevant to clinical services. However, there is a danger in this research strategy. It is quite possible that not all children with SLI are clinically identified and served within our service delivery systems. In such circumstances, there is the potential for systematic factors to influence which children do or do not find their way to clinical service.

Clinical Implications If our research questions are concerned with the characteristics of the actual population of children with SLI that exists in our communities and not just those who are being served, then we need to turn to methods of epidemiology to aid our research.