Mathematics knowledge for teaching plays an important role in school practice. However, research has mainly evaluated empirically the nature of this knowledge in the last two decades. The question, how teacher education and teaching practice contribute to mathematics knowledge for teaching has only been explored more recently. This chapter aims to discuss different descriptions and conceptualizations of the conception of mathematics knowledge for teaching from an international study using the large-scale study Teacher Education and Development Study in Mathematics (TEDS-M 2008) as example. In the first part of the paper, the main currently discussed theoretical models for the construct of mathematics knowledge for teaching are described. In the second part of the paper, the ways to empirically evaluate the different facets of this knowledge for teaching are described using items and descriptions from TEDS-M. The paper closes with prospects for further research.