The duALine project chose to examine the methods used to assess food sustainability in a chapter of its own, separa te from the sectorial approaches presented previously, so that this examination could be as open as possible. This chapter focuses in particular on the specifie issues posed by food vis-à-vis the methods currently used to measure sustainability. Under this approach, this chapter looks firstly at the complexity of food systems, then how the associated challenges of sustainability could be structured and fin ally presents sorne methods and indicators and the research questions they raise.