Research indicates that it is common for elementary teachers to possess limited mathematics content knowledge, high levels of math anxiety, and low levels of mathematics teacher efficacy. Assuming action research as the chosen methodology, this research study was developed with the ultimate goal of improving how elementary teachers in my district teach mathematics by providing professional development that would deepen mathematics content knowledge and lower math anxiety. More specifically, this study involved designing, implementing and studying a specific professional development experience for in-service elementary teachers in my district aiming to achieve these goals, as a means to address the following research questions: (1) What new insights can we gain about elementary teachers' knowledge of mathematics, their perceptions of themselves as learners of mathematics, and their perceptions of themselves as teachers of mathematics? (2) How effective are specific professional development activities in engaging elementary teachers in (a) learning about big mathematical ideas and (b) grappling with their math anxiety? A first professional development initiative was designed based on what we know from the literature about elementary teachers' mathematical content knowledge, math anxiety and mathematics teacher efficacy, as well as best practices in professional development. As too few teachers elected to enroll in this professional development, however, it was not possible to implement and study it as originally intended. A second action research cycle was then initiated, which consisted in gathering information about the reasons for the low enrolment and the perceived needs of elementary math teachers in the district, redesigning a professional development initiative that reflected what had been learned, and then implementing and studying that experience. Data on the implementation of this second professional development experience was collected from a variety of sources--including specific survey instruments, audiotapes and artifacts from the workshop sessions, as well as the researcher's journal and participants' feedback forms. Qualitative methodology was employed to analyze these data with the goal of uncovering emerging themes that could shed light on each of the research questions. Social constructivism, Bandura's theory of self-efficacy, NCTM's (2000) "Principles and Standards", as well as transformative learning theory provided the theoretical lenses informing the research study. [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.]