TEDS-M is a collaborative effort of worldwide institutions to study the mathematics preparation of future primary and secondary teachers. This study investigates whether what future teachers learn in teacher education leads to more effective knowledge of mathematics and mathematics for teaching. The lead centre is the International Study Center at Michigan State University, which along with the International Association for the Evaluation of Educational Achievement (IEA), the Australian Council of Educational Research, and national research centres (NRCs) in 17 countries, is analysing the costs of becoming a teacher prepared to teach mathematics, the policies governing mathematics teacher education (including recruitment, selection, certification and accreditation); examining curricula in teacher education and their correlation with primary and secondary school curricula; exploring program opportunities to learn, and analysing intended and achieved outcomes of teacher education programs.