Chapter 14, Mental and Behavioral Disorders, in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, defines a process for assessing permanent impairment, including providing numeric ratings, for persons with specific mental and behavioral disorders. These mental disorders are limited to mood disorders, anxiety disorders, and psychotic disorders, and this chapter focuses on the evaluation of brain functioning and its effects on behavior in the absence of evident traumatic or disease-related objective central nervous system damage. This article poses and answers questions about the sixth edition. For example, this is the first since the second edition (1984) that provides a numeric impairment rating, and this edition establishes a standard, uniform template to translate human trauma or disease into a percentage of whole person impairment. Persons who conduct independent mental and behavioral evaluation using this chapter should be trained in psychiatry or psychology; other users should be experienced in psychiatric or psychological evaluations and should have expertise in the diagnosis and treatment of mental and behavioral disorders. The critical first step in determining a mental or behavioral impairment rating is to document the existence of a definitive diagnosis based on the current edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders. The article also enumerates the psychiatric disorders that are considered ratable in the sixth edition, addresses use of the sixth edition during independent medical evaluations, and answers additional questions.