This chapter discusses the use of eye-tracking techniques in survey research. We start with a discussion of research questions that eye-tracking can help answer. We then present a brief overview and history of eye-tracking techniques, and give more details about the technologies that are currently most feasible for survey researchers. We continue with a discussion of the relative methodological, technical, and analytical advantages and disadvantages of eye-tracking over more traditional, indirect methods for tracking respondents behavior (such as measuring response times, recording changes in answers, and tracking mouse clicks and movements). Finally, we present a summary of a series of recent experiments in which respondents' eye movements were tracked while they were completing a CASI survey.