Nonword repetition (NWR) tasks have become popular in recent years as measures of phonological short term memory (PSTM) in research settings, and as potential markers of language impairment in clinical settings. This has increased interest in the subskills that potentially NWR performance. The current study investigated the influence of PSTM, vocabulary skills, articulatory output skills, literacy, and speech perception on NWR in children ages 4;0-6;5. Partial correlations and regression analysis were used to establish an in-depth picture of the skills that constrain NWR, and to differentiate the skills that underlie this measure when the language skills of test takers and the wordlikeness of NWR items were taken into account. Results indicated that both PSTM and vocabulary were independently related to NWR performance when the entire sample was considered. When the sample was divided by language scores, higher-scoring participants' NWR performance was influenced by PSTM, while vocabulary scores were related to NWR performance in lower-language scoring children. Wordlikeness of nonword items also affected the skills related to NWR performance, in that scores on highly wordlike stimuli were principally related to vocabulary skills, while scores on less wordlike stimuli were significantly related to PSTM only. These results indicate that despite its popularity as a measure of PSTM, NWR cannot be considered a monolithic measure of this skill in all cases. In general, NWR performance in the current study were influenced by both PSTM and vocabulary skills, and that influence varied with the language skill of participants and the wordlikness of NWR items. [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.]