English-medium instruction has become a lynchpin of the internationalization process in Spanish universities. However, it is striking that very little attention has hitherto been paid to both teachers methodological training and the study of interaction in EMI classrooms. This proposal endeavors to tackle these two questions through a painstaking analysis of the interaction that takes place in classes in which English is the medium of instruction. With this in mind, the study will scrutinize (i) the organization of the metadiscourse used by the teachers, (ii) the type of questions asked and how they impinge on the teacher/students interaction, (iii) the impact of pronunciation on interaction, and (iv) how both anxiety and motivation affect the use of the foreign language in such interactions. These four aspects play a paramount role when it comes to facilitating and maximizing knowledge transfer, as they help to pay the way to students’ access to knowledge, especially when the means of instruction is a foreign language.