Recent evidence suggests that preschool children learn the sound based regularities of the language and that this, in turn, facilitates acquisition of novel words. What remains less clear is whether children who are delayed in acquiring the sound system are able to capitalize on these same regularities to support word learning. The goal of this research project is to understand how children with phonological delays learn new words. Four studies are proposed to examine the influence of sound based regularities on word learning by children with phonological delays and to identify diagnostic measures that are sensitive to the ability to use sound based regularities to learn new words. The findings to emerge from the proposed research will provide evidence of the types of processing and representations that underlie word learning in clinical populations of children. Importantly, the specific aims of the proposed research project complement and extend those of the Pl's existing K23 award, The Mental Lexicon in Language Acquisition (DC04781). The existing K23 award focuses on word learning and representations in typically developing children, whereas the proposed research extends this work to a clinical population of children, namely children with phonological delays.