How can formative assessment be used as a means to support teacher professional learning? This book presents several studies, from different countries, on approaches to formative assessment of teachers, both before they start working, and during their careers. These approaches draw on insights from studies into effective teacher professional development. Together, the chapters in this book provide an overview of the various ways in which formative assessment may be used to support teacher professional learning, and shed light on choices that can be made in designing such assessments. The studies illustrate how teachers may perceive formative assessment methods, how their learning processes might unfold during formative assessment processes, and which struggles they may have to deal with during the process. The book furthermore addresses questions concerning the impact of formative assessments on teacher learning. As such, this volume provides theoretical as well as practical prospects, as well as challenging ideas for how formative assessment may move further towards being an effective means for supporting teacher learning. This book was originally published as a special issue of Teachers and Teaching: Theory and Practice.