This study measured the impact of core vocabulary selection and core vocabulary use on overall communication effectiveness and literacy. In this study, 30 kindergarten special education students, both male and female, who were enrolled in the Developmental Kindergarten program (a self-contained special education classroom) and Inclusive Kindergarten program (a regular education classroom that includes up to five students with IEPs), were given a core vocabulary intervention. Each participant had speech and language delay as part of their eligibility criteria outlined on their respective Individual Education Plan (IEP). The control group of 15 students received language intervention through services directly provided by the speech-language pathologist. The remaining 15 students received language intervention through services directly provided by the speech-language pathologist as well as through the utilization of a core vocabulary board during therapy sessions. The study explored the selection and use of a prescribed core vocabulary intervention over a period of one trimester in order to report its impact on the overall communicative effectiveness and literacy of language-delayed students using AAC. The study participants were provided with a pretest, speech and language therapy sessions where the intervention took place, and a posttest, which were all administered by a speech-language pathologist. Analysis of data determined that selection and use of a core vocabulary intervention had a statistically significant effect on the communicative effectiveness and literacy skills of students with language-delay that use augmentative and alternative communication (AAC). [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]