Upper extremity amputations are rated in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, Section 15.6, Amputation Impairment, where text, tables, and figures guide evaluators in combining proximal diagnosis-based impairments (DBIs) and proximal range-of-motion impairments. The AMA Guides provides impairment grids for lower and upper extremity amputations, which are divided into five impairment classes (0 through 4), and each impairment class is further divided (except class 0) into five grades (A through E), each with its respective impairment rating that is expressed as a percentage of the extremity. Determining impairment class, and thus the default value of impairment, is straightforward if the amputation occurred directly at one of the points in the relevant grid; if the amputation occurred at another point, the evaluator should consult the appropriate figure to assess how the specific level of amputation corresponds with impairment percentages. An individual's proximal problems may lead to an increase in the impairment value because of the application of grade modifiers. Except in rare instances of bilateral upper extremity amputation or when the patient is unable to wear a prosthesis for a lower extremity amputation, the evaluator usually uses the default rating value within the selected impairment class as the final percentage rating. Evaluators are advised to re-read the amputation section in the AMA Guides before conducting an amputation evaluation.