This volume was written primarily for teachers who have developed (or who are being encouraged to develop) an awareness ofand commitment to teaching mathematics for understanding. The research findings presented in these chapters suggest instructional implicationsworthy of these teachers' consideration. Often, the authors in this volume describe instructional practices or raise issues that have thepotential to broaden views of teaching and learning mathematics. These chapters provide interesting problems and tasks used in the authors'work that readers can use in their own classrooms.The volume can also be used with courses for preservice and inservice teachers, collaborative teacher study groups, and other professionalactivities. A hallmark of good research is its connection to the relevant literature in the field, and the authors of this volume havethemselves drawn from the research literature to inform their work. The reference lists accompanying these chapters can be useful resourcesand should not be overlooked. Most importantly for teacher education, this volume showcases the variety of ways teachers can becomeengaged in research, and we hope that readers will recognize that teacher research can be both accessible and beneficial in the preparationand professional development of teachers.This is not to suggest, however, that this volume is intended only for teachers and teacher educators. It is also intended to be aninteresting, informative resource for other researchers, school administrators, and policy makers. The research presented in this volume isintended to provide an opportunity for those outside the classroom to gain insight into the kinds of issues that matter to teachers, the ways inwhich those issues might be researched, and the contributions that classroom research makes to mathematics education.