This thesis aims at contributing to the research on academic conference paper presentations, particularly to the discussion sessions that follow them. The main purpose of this study is to explore the speaker's expression of evaluation in the discussion session of two specialised conference paper presentations in Linguistics and Chemistry from a multimodal approach. I set out to investigate evaluation in spoken academic discourse beyond the traditional linguistic approach to foreground the role of kinesics and paralanguage that co-occur with the linguistic expression of evaluation. To meet the objective of the thesis, the theoretical framework was embedded in techniques of genre analysis (Bhatia 1993, Swales 1990) and discourse analysis, including the theoretical orientations of systemic functional linguistics (Halliday 1978, 1985a), conversation analysis (Schegloff & Sack 1973), pragmatics (Brown & Levinson 1978, 1987), and multimodal discourse analysis (Kress & van Leeuwen 2001). This framework allowed me to identify the structure of the interaction, the rhetorical moves in which the interaction is organised, and finally the linguistic and multimodal expression of evaluation that articulates the rhetoric of the interaction.