The American Medical Association (AMA) Guides to the Evaluation of Permanent Impairment (The Guides) is used in the United States, Canada, and abroad to rate impairments for people with illnesses or injuries. To date, there are six editions of the Guides, with the first edition published in 1971. This chapter provides a review and critical analysis of each of the editions of the Guides. There have been important developments in the Guides since its inception, and this evolution is detailed. The chapter authors focus on those sections of the Guides most relevant to the work of psychologists and neuropsychologists, including an analysis of chapters pertaining to mental and behavioral disorders, the central nervous system, and pain. The chapter authors highlight the changes that have been implemented in each edition of the Guides, as well as aspects that might continue to pose challenges for psychologists and neuropsychologists when determining impairment ratings. To illustrate the real-world implications of the Guides, the chapter authors explore its use in specific jurisdictions and the relevant case law that influences the usage of the Guides. Through our analysis of the Guides and its use, the chapter authors hope to provide the reader with meaningful insights into its strengths and weaknesses.