Over the past 30 years, within forensic contexts there has been increasing interest in the use of assessments based on behavioural and implicit assessment processes. Eye‐tracking, the ability to identify and track where an individual is looking, has increasingly been used to infer underlying cognitive processes related to observed behaviour. Within forensic contexts, the ability to monitor where an individual is looking, and by implication what they are interested in, is increasingly being seen as one potential way to gain objective information about offender cognitions. Eye‐tracking has been used to study general factors related to sexual interest within non‐offending samples and is increasingly being used to assess inappropriate or deviant sexual interest in offending populations. This chapter overviews the concept of eye‐tracking as a methodology, describes a number of different areas where it has been used, and then discusses in more detail how eye‐tracking is currently being used to assess normal and deviant sexual interest.