In Québec, collaboration between student teacher trainers is directly connected with the quality of student teacher training. This expectation has implications for the inter-professional relationship between cooperating teachers and university supervisors. Their respective, yet distinct knowledge, when combined and confronted, can be challenging and rewarding for student teachers (Gervais & Desrosiers, 2005). However, exchanges and discussions are not always fruitful (Sanford & Hopper, 2000), which is considered the most detrimental factor in the student teacher training process (Kauffman, 1992). This paper presents the preliminary results of a study on the circulation of knowledge between the two trainers, on the nature of the knowledge expressed, and on the dynamics of this expression. Does the discourse of student teacher trainers reflect the sharing and joint formulation, even co-construction, of knowledge (Martinaud, 2001)? Data was collected using audio recordings of conversations between trainers in the natural setting of secondary teacher internship. Drawing from Pelpel’s (2002) functions of trainers, analysis helped to identify and structure shared knowledge. Verbalization of knowledge appears to depend on the dynamics of knowledge sharing.