Two international studies that aim to assess students’ knowledge and skills in mathematics have won a prominent place in the global educational world: Programme for International Student Assessment (PISA) and Trends in International Mathematics and Science Study (TIMSS). While these studies come with numerous works describing their frameworks, and while a lot of research in edumetrics, sociology and educational sciences have been published, what light the mathematics didactics can place on them? After a short outline of their frameworks, we will make use of two different approaches, both being based on a priori analysis of the tasks for analysing the content of the assessments and for reinterpreting the results. The first approach, labelled didactical and cognitive, is associated with the implicative statistical analysis and allows a new look on the PISA results as well as on comparisons between countries. The second, nested in the didactical anthropological theory, addresses mainly TIMSS content and the distribution of its assessment items in relation to a given mathematical syllabus.