In many workers’ compensation systems, shoulder injuries are among the most common reasons for filing a claim, and greater familiarity with the significant differences in rating processes between the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth and Sixth Editions will help physicians avoid common pitfalls and improve the reliability of impairment ratings. One source of confusion associated with rating a shoulder is determining whether to use the range-of-motion (ROM) method or the diagnosis-based impairment (DBI) method. The AMA Guides, Sixth Edition, clearly states that DBI is the primary method of evaluation for the upper limb and that range of motion is used primarily as a physical examination adjustment factor and only when a grid permits its use as an option. An impairment rating that is calculated using ROM may not be combined with a DBI-based impairment rating; DBI is the primary method, and ROM should be used “only under specific circumstances.” When measuring ROM, evaluators should record all six measurements of shoulder motion for each arm and use the injured arm as a baseline. If two or more diagnoses are possible under the DBI method, evaluators should choose the highest causally related impairment rating from the shoulder grid and modify the clinical studies grade modifier.