Teacher leadership has gained attention in recent years as a plausible means by which educational reform and instructional improvement can be accomplished through ongoing, site-based professional development for teachers. This article reviews and draws conclusions across the research literature on professional development and teacher leadership to examine a conceptual connection: professional development leads to teacher leadership, which leads to further professional development for the teachers enacting leadership and their colleagues. The article draws heavily on recent work done in the United States, but also includes international perspectives. Insights on the literature and implications for professional development policy are also discussed. (Contains 1 figure.)