In this article, the authors present a definition for co-teaching. They argue that co-teaching has the potential to be an effective arrangement for attending to student learning, preparing a teacher candidate to enter the profession, and eliminating some of the snags and pitfalls associated with traditional student teaching. In addition, they identify and describe six models of co-teaching along with examples of how these models may contribute to student learning in a Professional Development School (PDS). They conclude by suggesting areas for further research on the effects of co-teaching. (Contains 1 table.)