"The Construction of New Mathematical Knowledge in Classroom Interaction" is a scholarly book that focuses on the specific characteristics of mathematical communication in the classroom. It examines how mathematics instruction can be designed as a learning environment in which students acquire mathematical insights and competencies through the initiatives, offerings, and challenges posed by the teacher. The book explores how new mathematical knowledge is interactively constructed in the typical communication between educators and learners. To answer these questions, theoretical perspectives on mathematical knowledge and communication are developed and qualitatively analyzed. The careful analysis of several classroom episodes in elementary school is based on an epistemologically oriented approach that has been developed over the years by Heinz Steinbring. This methodological approach is systematically presented and applied in the book to capture and describe the quality of mathematics instruction.