In this study I have profiled the background experiences, academic preparation and perceptions of a small number of cooperating teachers in a secondary Professional Development School site about their experiences in successful practice. The results indicate that cooperating teachers have a depth of understanding of their role in the process and that they undertake the responsibility with clear expectations for the experience. The data reveal four conditions, some that are commonly known and some that extend the understanding of the role of cooperating teachers in teacher preparation, that support successful practice. The organizational structures of the particular PDS lay the foundation for the creation of zones of pedagogical construction. Most significant is the distinction between the conceptions and performance of maestros and mentors that emerges through their description of their roles.