Lesson study is a professional development process that teachers engage in to systematically examine their practice, with the goal of becoming more effective. Originating in Japan, lesson study has gained significant momentum in the mathematics education community in recent years. As a process for professional development, lesson study became highly visible when it was proposed as a means of supporting the common practice of promoting better teaching by disseminating documents like standards, benchmarks and nationally validated curricula. While the body of knowledge about lesson study is growing, it remains somewhat elusive and composed of discrete research endeavors. As a new research area there is no coherent knowledge base yet. This book will contribute to the field bringing the work of researchers and practitioners together to create a resource for extant work. This book describes several aspects of Lesson Study, amongst others: it gives an historical overview of the concept, it addresses issues related to learning and teaching mathematics, it looks at the role of the teacher in the process. The last two sections of the book look at how lesson Study can be used with preservice mathematics teachers and at university mathematics methods teaching.