ABSTRACT Speech is a critical aspect of the human experience and usually develops in a “seemingly automatic process that continues from birth through adolescence (p.1, NAM, 2016)” and underlies many related abilities (e.g., language and reading, see National Academy of Medicine Report on Speech and Language Disorders, 2016). Many individuals with Down Syndrome (Trisomy 21, DS) struggle to communicate and participate more fully in human communication and educational learning experiences because their speech is difficult to understand. The purpose of the proposed project is to measure speech-articulation accuracy and speech intelligibility, and their proposed primary predictors at study entry in 20 children with DS age 7;0 to 12;11. A validated treatment, speech recast intervention (see Yoder, Camarata & Woynaroski, 2016) will be used to drive growth in speech intelligibility as a means of evaluating changes in potential sequelae of change. This integrated study will include measures of speech- articulation accuracy, speech-prosody, general cognitive ability, receptive vocabulary skills, and clinical assay of oral-motor ability as potential predictors of speech intelligibility growth in DS. We will also be measuring suprasegmental and rhythmic factors associated with growth. The results of this study will provide important information on factors that contribute to intelligible speech in DS and subsequently provide the basis for refining and future intervention investigations of treatment for speech deficits in children with DS.