This study explores the interactional unfolding of 'epistemic status check' (ESC) (e.g. 'no idea?', or 'you don't know?'), which is a frequently observed feature of teacher talk in language classrooms. The paper aims at contributing to the literature of institutional interaction and classroom discourse by introducing and defining 'ESCs', which also will indirectly be conducive to expanding the scope of the idea of epistemic engine (Heritage, 2012a,b). An ESC can be defined as a speaker's interpretation of another interactant's state of knowledge, which (in the case of classrooms) can be initiated in order to pursue certain pedagogical goals when a second-pair part of an adjacency pair is delayed. It is employed subsequent to inter-turn gaps (Schegloff, 2007) that are accompanied by non-verbal cues. The study draws on 16 h of video-recorded interactions in two English language classrooms in a public school in Luxembourg. The participants are adolescent multilingual students, aged between 15 and 18, and a local teacher. The analysis was carried out using conversation analysis, by also drawing on the use of multi-semiotic resources including gaze directions, gestures, and body orientations. The findings show that teachers treat these embodied actions as displays of insufficient knowledge in classroom talk-in-interaction, and initiate ESCs subsequent to certain student non-verbal cues including gaze withdrawals, long silences, and headshakes. These displays of insufficient knowledge were found to be visual resources that the teacher uses in order to move the classroom activity forward, by first initiating an ESC, and then by allocating the turn to another student. These findings have implications for the analysis of 'claims of insufficient knowledge' (e.g. 'I don't know') in general and their management in instructed learning environments in particular. (C) 2012 Elsevier B.V. All rights reserved.