The paper is based upon a case-study of mentoring in teacher education in Norway. It describes the practice of the cooperating teacher and how mentoring in the practice-field contributes to student teachers learning. The main focus is how student teachers develop pedagogical content knowledge in mathematics through reflections with the mentor about their teaching episodes. The study draws attention to how Vygotsky's and others' ideas about scaffolding and assisting in the Zone of Proximal Development (ZPD) can be useful in understanding how student teachers learn to teach mathematics. This paper specially focuses the role of imitation and modelling. (Contains 8 footnotes.) [For complete proceedings, see ED500858.]