The purpose of this chapter is twofold. On the one hand, our goal is theoretical, as we aim at providing an instrument for detecting, analyzing, and solving ambiguities based on the reasoning mechanism underlying interpretation. To this purpose, combining the insights from pragmatics and argumentation theory, we represent the background assumptions driving an interpretation as presumptions. Presumptions are then investigated as the backbone of the argumentative reasoning that is used to assess and solve ambiguities and drive (theoretically) interpretive mechanisms. On (...) the other hand, our goal is practical. By analyzing ambiguities as stemming from different presumptions concerning language or, more importantly, expected communicative roles and goals, we can use communicative misunderstandings as the signal of deeper disagreements concerning mutual expectations or cultural differences. This argumentation-based interpretive mechanism will be applied to the analysis of medical interviews in the area of diabetes care, and will be used to bring to light the sources of misunderstanding and the different presumptions that define distinct cultures. We will consequently illustrate the analytical tools by identifying and distinguishing the various types of ambiguity underlying misunderstandings, and we will address them by describing the communicative intentions ascribed to the ambiguous utterances. (shrink)