This chapter summarizes the impact that international comparisons have had on education policy in Western countries, with the focus on mathematics. It considers the success of taking strategies from mathematically high-performing countries and implementing them in the UK and elsewhere. The chapter also considers both international comparisons based on rigorous testing of learners at a particular age group and also the importing of strategies from mathematically high-performing countries into other countries and, in particular, into England. There is no doubt that international comparisons in mathematics are feasible to undertake and are useful and informative for the countries involved. The two well-respected international tests, Programme for International Student Assessment (PISA) and Trends in International Mathematics and Science Studies (TIMSS), have had a considerable impact on policy in many countries, including the UK.