The AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Chapter 14, Mental and Behavioral Disorders, focuses on the particularly challenging process of evaluating a person with a mental or behavioral disorder. This chapter is unique: It does not include numeric impairment ratings because no precise methods exist for assessing impairment in mental disorders. This article focuses on the process of gathering qualitative data and relevant information to substantiate the behavioral impairment assessment, for which the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition–Text Revised (DSM-IV-TR) is used. Impairment ratings in the AMA Guides reflect “consensus-derived estimates that reflect the severity of the impairment and the degree to which the impairment decreases an individual's ability to perform common activities of daily living [ADL]” and designates four relevant areas to consider: ADL; social functioning; concentration, persistence, and pacing; and deterioration or decompensation in complex or work-like settings. The validity of an impairment classification depends on the process used to collect and analyze the data, including clinical treatment records, hospital discharge summaries, community mental health program activity reports, patient and family interviews, reports from work evaluation or rehabilitation centers, supported employment records, and workplace evaluations. Defining maximum medical improvement in patients with mental and behavioral disorders is difficult and, in some instances, may be impossible.