Over the past thirteen years, physicians have experienced a learning curve regarding how to use the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) with a “California flavor.” Physicians are mandated by law to provide the court with the “most accurate” ratings that apply in a given case based on permanent objective medical evidence and the education, skills, knowledge, and experience of the physician. Two cases, commonly known as Almaraz–Guzman, profoundly changed how California interprets and uses the AMA Guides, Fifth Edition. Under Almaraz–Guzman, the evaluating physician is tasked with first providing a whole person impairment using a “standard” AMA Guides impairment rating. If the physician believes that this rating “is not the most accurate” and does not adequately reflect the extend of the disability, an alternative rating “within the four corners” of the AMA Guides can be provided based on “reasonable medical probability.” In many cases, this has resulted in the use of tables, charts, methods, measurements, and descriptions from chapters and text materials that were not originally intended to apply to other parts of the body. The AMA Guides tells us that when there is no clear impairment rating, rating by analogy or use of other impairments that create a similar effect on ADLs should be considered, and the opinion must reach the level of substantial evidence.