Collaboration is becoming increasingly important in the realm of education (Novoa, 2004). For instance, as soon as training is undertaken, the future teacher must develop an ability to cooperate in a pedagogical context. However, in order to learn to make a relevant contribution to a teaching team's undertakings and to provide innovative suggestions in pedagogical matters (Gouvernement du Quebec, 2001), the student teacher needs solid backing from the cooperating teacher. A student teacher's willingness to reflect on and to question his own teaching practices will create a much more promising learning context (Portelance & Durand, 2006). Reciprocally, the cooperating teacher will make a positive contribution to the student teacher by accepting that his positions be questioned and even altered (Johnston, Wetherill & Greenebaum, 2002). It is the dynamics of sharing of knowledge and know-how in this partnership that retains our interest. From 2004 to 2007, the researchers carried out a study of the subject by examining four practicum sessions at high school level in a number of Quebec schools. To gather data, the researchers used written questionnaires, individual interviews, as well as recordings of conversations between student teachers and their cooperating teachers. These conversations pertain to the conception and to the execution, by the student teacher, of teaching-learning situations. These dialogues were integrally transcribed and processed by N'vivo, software designed to analyze qualitative data. the researchers present a typology of the respective roles taken on by the two partners in their discussions. The cooperating teacher reveals himself to be an advisor, a transmitter of information and a teacher. The student teacher also takes on the role of transmitter of information, as well as that of reflective practitioner, among others. the researchers observed that the conversations are usually carried out in an egalitarian spirit and, in some cases, give rise to co-construction of practical knowledge.