Dissociation is a neurobiological response to persistent and/or extreme threat. Dissociation may be present across a variety of psychological conditions but is most severe in trauma-related disorders including dissociative disorders. Given the overall lack of training on complex posttraumatic reactions and dissociation in most graduate programs, it is likely that even classic symptom presentations will be missed or misinterpreted. The authors provide background information on dissociative and related disorders. This chapter primarily focuses on the various procedures for gathering diagnostic information relevant to dissociation including screening, interview, self-report, and performance-based methods. Case presentations are offered to highlight the complexity of evaluating dissociation in clinical contexts. A brief overview of the literature on feigned presentations is also discussed to help inform clinicians who may be working in settings where exaggeration is more likely (e.g., forensic settings). The authors emphasize the importance of building the therapeutic relationship and understanding that additional disclosures and observations of dissociation may emerge over time as an alliance is formed.