The need for a competent teaching force as a warrant for high quality education remains a central concern in many countries. Paradoxically, research focusing directly on the professional knowledge of teacher educators remains scarce. The implicit assumption is that a teacher educator simply teaches (his/her subject) in higher education and that teaching novice teachers does not require any additional preparation or expertise. As a result, a research-based understanding of teacher educators' professionalism is missing. This project addresses this knowledge gap and focuses on how teacher educators make sense of their work and enact their expertise. More specifically, we will study the content of teacher educators’ professionalism by looking at how it actually operates in practice. Drawing on positioning theory, we frame teacher education practices as discursive practices in which teacher educators position both themselves and their student teachers in particular ways. These positionings strongly impact student teachers' (possibilities for) learning. Data collection includes videotaping of teacher education practices, biographical interviews (with teacher educators), questionnaires (with student teachers), and document analysis. This project will result in a systematic conceptualization of teacher educators' professionalism which is new to the field and offers a strong basis for future research. Results will also have direct knowledge utilization purposes for teacher educators themselves by opening powerful perspectives for them to understand possible threats to the effectiveness of their practice and actively work towards its improvement.