The research literature on middle grades mathematics teachers' mathematical literacy indicates that mathematical problem solving and problem posing are essential skills for mathematics instruction, and that teachers must be skilled in mathematical problem solving and mathematical problem posing. However, it is not well known how these two skills affect the classroom experiences of middle grades mathematics teachers, nor is it known how those teachers perceive these skills as affecting them. This basic qualitative study examined the mathematical problem-solving and mathematical problem-posing experiences of middle grades mathematics teachers and their perceptions of the impact those have within their classrooms. The experiences of nine middle grades mathematics teachers located in the East South Central region of the United States were investigated through face-to-face interviews, classroom observations, and problem-solving and problem-posing activities. Collected data were analyzed through thematic analysis and synthesized in order to identify the themes present. Five major themes occurred through the analysis; those themes are the importance of real-world applications, conceptual understanding, instructional strategies, procedural fluency, and self-efficacy. These themes reinforce the theoretical framework for the study, which focused primarily on Schoenfeld's mathematical problem-solving theory and was supported by Bruner's constructivist theory and Dewey's learning by doing theory. Additional research examining the training that leads to middle grades teacher licensure is recommended, along with research that includes more classroom observations and a quantitative component that measures the skills of participants. [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.]