This program of research is designed to explore the status of the lexicon in young children with specific language impairment (SLI). The research plan is based on the premises that: (1) the lexical production problems of children with SLI are rooted in deficits in lexical storage; (2) comparisons between children with and without SLI can be used to characterize the nature of lexical storage deficits associated with SLI and (3) a more complete understanding of these lexical storage deficits will lead to more efficacious treatment for lexical production in children with SLI. Participants are 20 preschoolers who have SLI, their 40 normally-developing age-matched cohorts and their 40 normally- developing, younger, language-matched cohorts. These experiments are motivated by Levelt's (1991) speech production model, and, in particular, his notion of lemma and lexeme representation and access. Specifically, it is hypothesized that the lemma is particularly underdeveloped in children with SLI and that this proble may be traced back to atypical semantic mapping during early word learning. Four experiments are designed to investigate the organization and elaboration of the semantic lexicon. A fifth experiment is designed to determine what semantic information is initially stored when children with SLI and their cohorts map new words. A sixth experiment will test the efficacy of intervention aimed at improving lexical production for children with SLI by enhancing their semantic knowledge.