The purpose of this study was to better understand the process of mathematics teacherdevelopment. More specifically, in this study, I examined how mathematics teachers make senseof their professional development experiences in the context of their practice. Goldsmith andSchifters (1994) model for the development of mathematics teaching provided a researchframework from which to view mathematics teacher development. They suggest fourcomponents that should be taken into consideration when examining mathematics teacherdevelopment: qualitative reorganizations of understanding, orderly progression of stages,transition mechanisms, and motivation and disposition.The population under study was practicing mathematics teachers engaged in aprofessional development program who experienced changes in their knowledge and beliefsabout mathematics, mathematics teaching, and/or mathematics learning. Data were collectedduring a week-long summer institute and the subsequent year of teaching. Data sources includedobservations, interviews, and teacher products (such as open-ended surveys and journals). Thedata were analyzed to determine how three teachers made sense of their professionaldevelopment experience (a) from their practice; (b) for their practice; and (c) in their practice.The research framework guided generalizations of the process of mathematics teacherdevelopment. The results showed that teachers construct different understandings from the sameexperiences, and thus professional development is not entirely about the curriculum. Rather,professional development should be concerned with providing opportunities for teachers ofvarying backgrounds to interact with their prior knowledge and beliefs. Also, this study pointstoward the importance of teachers initial goals and the dispositions of persistence, courage, andthe desire to be different in initiating and sustaining development.A model of the dynamic relationship between changes in understanding and changes inpractice is offered and a critique and modification of the research framework is provided.Because much of how teachers make sense of their professional development experiences ismissed when professional development is not thought of in the context of their prior, intendedand actual practice, recommendations for those concerned with how mathematics teachersdevelop include not relying solely on teachers self reports at the conclusion of a professionaldevelopment experience.