This article uses the notion of professional identity within the framework of actor network theory to understand didactic practices within three faculties in an institution of higher education. The study is based on a series of interviews with lecturers in each faculty and diaries of their didactic practices. The article focuses on the use of a multiple-choice assessment tool available on a virtual learning environment and on the lecturers' attitudes towards it. The data suggest that the prevalent epistemic culture in a faculty's community of practice plays a significant role in the choices made by lecturers as far as their actual use of the tool is concerned. The lecturers' professional identity is also a substantial element in shaping their attitude towards the tool. (Contains 1 note.)