Research on nature of science (NOS) and scientific inquiry (SI) has indicated that a teacher's knowledge of each, however well developed, is not sufficient to ensure that these views necessarily manifest themselves in classroom practice (Lederman & Druger, 1985; Lederman, 2007). In light of the considerable research that has examined teachers' subject matter knowledge structures and their classroom practices (e.g., Gess-Newsome & Lederman, 1993, 1995), what was conspicuously absent from the research on teachers' NOS- and SI-related classroom practice was an assessment of teachers' knowledge structures for NOS and SI. As such, the current investigation developed case studies of four high school physics teachers with the intent of inferring their classroom practice knowledge structures for NOS and SI across 15 targeted aspects. These results were then compared to responses communicated through the "Knowledge Structures for NOS and SI ("KS4NS") questionnaire". The degree of congruence between the two instruments was gauged at the level of included concepts, connections between them, and also for other structures or thematic elements. In addition, the results from the "KS4NS" were compared to teachers' conceptions expressed through more traditional instruments for assessing NOS and SI, in this case the "Views of Nature of Science" ("VNOS") questionnaire and the "Views About Scientific Inquiry" ("VASI") questionnaire, respectively. The results of the current study indicate a limited congruence between teachers' knowledge structures for NOS and SI and those espoused in their classroom practice, most notably at the level of the connections between constituent aspects, as few were evidenced in teachers' instruction. In addition, there is indication that the "KS4NS" questionnaire is more attuned to identifying those specific aspects of NOS and SI most likely to evidence themselves in teachers' classroom practice. The necessity of having teachers explicitly reflect on the structure of the subject matter they are learning for teaching is reiterated through the findings of the current study. The utility of the "KS4NS" as tool to foster teachers' reflections on their conceptualization of NOS and SI independent of, or in conjunction with, traditional subject matter also warrants further investigation. [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.]