Drawing on interviews with clinical and university-based teacher educators and administrators, the authors explore the challenges of building and sustaining collaborative university/school partnerships. Using the concept of ''communities of practice'' (Communities of practice: learning, meaning, and identity, Cambridge University Press, Cambridge, UK, 1998), the authors describe how clinical and university-based teacher educators share a set of assumptions about their respective roles--described as a form of ''collusion''--that confirms status differences as well as the value of transmissive models of teaching. These assumptions undermine the goal of collaboration. The authors argue that the process involved in forming university/school partnerships needs to be understood less as an administrative and motivational problem than a question of identity formation and of relationship building.