G iven the potentially profound influences of psychological variables on the experience, expression, and treatment of medical conditions (Turk & Melzack, 2001), it is critical to efficiently and adequately assess such factors in medical settings. The Personality Assessment Inventory (PAI; Morey, 1991) is commonly used for this purpose. However, although research on the PAI in medical settings has expanded dramatically during the last several years, the overall research base remains relatively limited. Furthermore, most existing research has focused on particular populations such as those with chronic pain, nonepileptic seizures, and head injuries, or specific applications such as the validity of neuropsychological data. As a result, clinical recommendations for using the PAI in such settings must be relatively tentative. The purpose of this chapter is to briefly review published studies and provide suggestions for using the PAI with medical patients based on the literature and the clinical experience of the first author, who has been using the PAI with chronic-pain patients for more than 6 years.