Chapter 16, The Upper Extremities, in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth Edition, presents several changes from the Fourth Edition. The changes are minor compared to those in Chapter 15, The Spine, but are more significant than those in Chapter 17, The Lower Extremities. This article examines some of the most important revisions, notably the more rigorous standards for upper extremity evaluation, the requirement to compare motion findings to those of the contralateral extremity, entrapment neuropathies evaluation, and strength assessment. The principles of assessment are essentially unchanged in the AMA Guides, Fifth Edition, and Section 16.1c now clarifies the process of combining assessments. The Fifth Edition provides more direction about how to measure motion, but the values for motion deficits remain the same as in the Fourth Edition. Among important changes in the Fifth Edition regarding rating peripheral nerve impairment are: grading sensory deficits, rating entrapment neuropathies, and evaluating complex regional pain syndrome. The most noteworthy changes in assessing impairment due to other disorders are the following: explicit directions about how to rate these other disorders; elimination of rating for joint crepitation; inclusion of new radiographic criteria for rating carpal instability, and introduction of a new process for rating shoulder instability. The discussion of strength is expanded in the Fifth Edition of the AMA Guides.