Featured prominently in recent federal education regulations, the term "job-embedded professional development" has come into increasingly common usage for more than a decade, yet rarely is it explicitly defined. But what exactly is job-embedded professional development? What types of teacher learning opportunities count as being job embedded? How might job-embedded professional development improve teaching practices and student learning outcomes? What does the research say about it, and how can states and districts implement it well? In this Issue Brief--written in collaboration with the Mid-Atlantic Comprehensive Center and the National Staff Development Council--the National Comprehensive Center for Teacher Quality (TQ Center) intends to answer these important questions with a focus on job-embedded professional development for teachers only (not for other educators such as principals). (Contains 2 tables.) [This report was written with Joellen Killion.]