This chapter draws on data and findings from several video studies to describe the quality of mathematics teaching in Switzerland. The focus is on features of instructional practice and quality as core components of classroom behavior that reflect the teacher's expertise in creating optimal learning opportunities. The didactic triangle is used as the basis for describing the profile of expertise in Swiss mathematics instruction in terms of three interdependent dimensions of instructional quality. A core element of this pofile can be identified in Swiss mathematics teachers' particular strengths in the culture of communication, support and relationships. Findings also paint a generally positive picture of the culture of teaching, learning and understanding (e.g., methods and choreography of teaching) in Swiss mathematics classrooms. However, the culture of objectives, materials and tasks proves to be rather average in international comparison in several respects (level of mathematical content, characteristics of the problems set and the way they are worked on in lessons). In particular, there seems to be room for improvement in the specific context of the didactics of mathematics (e.g., the level of cognitive and mathematical challenge) Abstract This chapter draws on data and findings from several video studies to describe the quality of mathematics teaching in Switzerland. The focus is on features of instructional practice and quality as core components of classroom behavior that reflect the teacher's expertise in creating optimal learning opportunities. The didactic triangle is used as the basis for describing the profile of expertise in Swiss mathematics instruction in terms of three interdependent dimensions of instructional quality. A core element of this profile can be identified in Swiss mathematics teachers' particular strengths in the culture of communication, support and relationships. Findings also paint a generally positive picture of the culture of teaching, learning and understanding (e.g., methods and choreography of teaching) in Swiss mathematics classrooms. However, the culture of objectives, materials and tasks proves to be rather average in international comparison in several respects (level of mathematical content, characteristics of the problems set and the way they are worked on in lessons). In particular, there seems to be room for improvement in the specific context of the didactics of mathematics (e.g., the level of cognitive and mathematical challenge).