The purpose of this study was to investigate the use of linguistic knowledge in spelling by analyzing spelling errors made by 220 students in the fourth, fifth, and seventh grades. A 25-word researcher-designed spelling test with considerations of word frequency, word familiarity, and word type (based on morphological complexity) was administered. An error coding system was established based on the Triple Word Form theory. Each misspelling was coded based on its linguistic features and scored cumulatively in 3 categories: Phonological Representation, Orthographic Legality, and Morphological Legality. The error coding system revealed the linguistic profiles of misspellings and allowed the comparisons among subgroups matched on grades, reading, and spelling ability levels. The results of profile analyses supported the Overlapping Waves Model, which advocates that spellers use their phonological, orthographic, and morphological knowledge in spelling simultaneously regardless of age, reading, or spelling levels. On the other hand, the study did not find evidence supporting the stage-specific theory, which defines each stage by observations of the consistent use of one strategy in spelling. The linguistic profiles revealed the competition between Phonological Representation and Orthographic Legality, which provided little evidence supporting the specific phonological deficit hypothesis. On the contrary, the researcher found that the key to becoming an average speller is to be able to effectively apply sufficient phonological knowledge in spelling. For students with poor reading ability, they do not just suffer from limited phonological knowledge but also from the lack of other linguistic knowledge. For any two students with average reading ability, it is the one who can apply sufficient phonological knowledge that benefit in spelling and perform at the level that matches his or her reading ability. Educational implications are discussed. [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.]