The central purpose of this three-paper dissertation was to explore the ability of school-age children with and without language-learning disabilities (LLD) to apply sound/word level structure knowledge when performing speaking, spelling, and reading tasks. Data came from a larger investigation that used stratified sampling to create two ability groups--children with typical language (TL) and with LLD--comparable in terms of age (range 6 through 18 years), sex, race/ethnicity, and socioeconomic status. The first study addressed questions about whether a short probe of nonword stimuli that are more wordlike (contained true morphemes) or less wordlike (contained no true morphemes) are better suited for discriminating the spoken word repetition abilities of students with TL and LLD at different ages. Both word lists differentiated children with TL and LLD with large effect sizes at all four age levels, and both appear to have diagnostic value. The second study examined relationships of nonword processing performance in students with and without LLD across the three tasks of nonword speaking (repetition), spelling, and reading with two additional variables, phonemic awareness (PA) and vocabulary awareness (VA). Regression analysis showed that PA was associated significantly with all tasks for LLD students and with reading and spelling for students with TL. VA was associated significantly with all tasks for TL students, but only with nonword spelling for students with LLD. In the third study, fine-grained error analysis was used to describe error profiles (phonemic, orthographic, and morphemic) for TL and LLD on nonword spelling and reading tasks. At the elementary level, both groups made significantly more morphemic errors in spelling than reading; also, students with TL made significantly more orthographic errors in spelling than reading. At the secondary level, the LLD students exhibited significantly more phonic and morphemic errors in spelling than in reading. Thus students with LLD appear to exhibit error patterns that are qualitatively different and go beyond simple differences in degree from students with TL. Collectively, these studies contribute to understanding of sound/word level structure knowledge in oral and literate tasks. Findings have practical implications for designing assessment measures and intervention programs targeting inter-modality abilities. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]