The PISA items are first written in French or English, and then translated into the language of instruction in the different countries where they are submitted. In this respect, translation issues are crucial, whether lexical or grammatical. A translation guide is provided by the OECD. However, in the section of the guide devoted to mathematics, there is no mention of grammatical issues, despite their critical nature for the teaching of mathematics. We hypothesize that this lack of interest is likely to lead to biases in the interpretation of students' answers that might skew the statistical results provided by the OECD, in particularly for those students whose mother tongue is not the language of schooling. The aim of the workshop is twofold. Firstly, we wish to share our methodology and our initial results involving the analysis of a few items and a small number of languages spoken in Europe. This has enabled us to identify some tensions resulting from the legitimate desire to remain close to the sy