This chapter will provide readers with an overview of a professional development created and enacted to support teachers' implementation of high cognitive demand tasks (Smith & Stein, 2011). This multiple case study seeks to give voice to the three seventh grade mathematics teachers who participated in the professional development as they share their perspectives on what factors affected their implementation of high cognitive demand tasks. The goal of this chapter is to provide an overview of the structure of the professional development, share the aspects of the professional development the teachers identified as supportive when planning and implementing high cognitive demand tasks in their mathematics classrooms, and discuss ideas for future professional development aimed at providing teachers with instructional practices to incorporate into classrooms.