Critical analysis of the literature reveals that many questions about the knowledge and practice of mathematics teacher educators (MTEs) remain in need of further research: how do they know what to teach; how do they learn how to teach teachers; how do they prepare to teach their courses; how does the research on teacher education inform their practice? Using a multiple case-study research design, this study examined the professional work of four MTEs as they planned for, taught, and reflected on mathematics content courses for pre-service elementary teachers. Across one semester, data were collected from multiple sources, including interviews, classroom observations, and documents. Data were analyzed within a goals-knowledge-practice framework. For each of the four instructors, the framework portrays the complex and interactive nature of their knowledge, goals, and practice. Key to understanding these complex interactions was understanding the role of various ideologies--about teaching, about learning, about students, about practice, about knowledge, and about mathematics--that were expressed by the MTEs in their narratives and actions. This study contributes to existing research on the knowledge base of mathematics teacher educators by presenting evidence-based understandings and characterizations of goals, knowledge, practices, and ideologies. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]