This article describes a qualitative study into student teachers' learning processes through changes in their interactive cognitions. First, theoretical propositions about the relation between learning to teach, professional development, and practical knowledge are defined. Next, the procedure to grasp interactive cognitions as part of practical knowledge is explained. On three moments during teaching practise, students were video-recorded while teaching and then audio-taped during a stimulated recall interview. Changes in students' interactive cognitions are understood as indicators for learning and professional development. The results show substantial differences between students. The significance of the findings for teacher education research is illustrated.