Teacher leaders are teachers who aspire to stretch beyond their classrooms to engage in leadership roles that take many shapes and forms, both "informal" and "formal". These teachers view the school as a whole, see the "big picture" and focus on how they can help improve aspects of the school to result in increases in student achievement. Teacher leaders see themselves as "teachers" first and do not want to become principals or administrators, but want to work collaboratively with their colleagues and school administrators to improve school and student performance. This issue of "The Progress of Education Reform" will discuss the roles teacher leaders can play; how they can contribute to overall school and student success; how some states are formally supporting teacher leaders and the concept of teacher leadership; and policy implications and recommendations for state policymakers on how to explore and/or expand teacher leadership in their states. (Contains 4 endnotes.)