Abstract: In the area of Psycholinguistics, eye-tracking has been a successful and valuable tool for the investigation of on-line processes of language comprehension and language production (e.g., [Griffin and Bock 2000], [Tanenhaus et al. 1995]). However, the application of eye-tracking to the investigation of mechanisms underlying more naturalistic language use, e.g. dialogue, has so far been limited to the examination of eye-movements of either the speaker or the listener in isolation (e.g., [Brown-Schmidt et al. 2005]; [Richardson and Dale 2004]). Even offline dialogue experiments investigating, e.g. priming effects, usually involve only one "real" participant while their interlocutor is a confederate of the experimenter. In order to test predictions coming from dialogue models (e.g., [Pickering and Garrod 2004]) and in order to provide the kinds of evidence necessary for their further development, experimental methods that directly examine behaviour of participants actually engaged in a conversation are needed. Additionally, eye-tracking measures established in psycholinguistic monologue research need to be compared with their dialogue processing counterparts. Furthermore, new measures describing the relation between speaker and listener eye-movements in communication are needed, as they can give rise to the language mechanisms underlying conversational interaction.