This chapter reports on different eye tracking applications in general use and makes a distinction between non-interactive and interactive ways of using eye tracking to study translation, translators’ use of technology, as well as in usability and reception studies. Then follows a section on eye tracking technology and theory introducing the basics of eye tracking technology and the assumed relation between eye movements and cognition, with an account of the most frequently used measures in eye tracking methodology. The beginnings of eye tracking in relation to reading and translation are then surveyed, first focussing on how differently translators move their eyes when translating from the way readers normally read text. This leads to a more detailed treatment of eye movements during post-editing of machine-translated text, during subtitling, and when working across an interactive interface. Here, focus is on the cognitive effort involved. The next main section treats two main challenges to using eye tracking, viz. the fundamental question of connecting gaze data with cognitive facts and the question of reactivity effects in the recorded gaze data. The conclusion affirms the relevance of using eye tracking as a non-interactive research tool, possibly in a mixed-methods design with qualitative data and neuroscience technologies.