This article is the third in a series of four that explore the effects of age-related changes in impairments as defined by the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Fifth and Sixth Editions. Specifically, this article focuses on evaluation of disturbances of the nervous system, divided for discussion here into four parts—the central nervous system (CNS), the peripheral nervous system, vision, and hearing—and offers guidance in using the AMA Guides, Fifth and Sixth Editions, in a variety of specific disorders within each group. For example, the CNS discussions address disorders of consciousness and awareness; sleep and arousal disorders; alterations in metal status, cognition, and highest integrative function; aphasia or dysphagia; emotional or behavioral disorders resulting from CNS causation (fifth edition only); chronic pain; and others. One of the most challenging issues in evaluating peripheral neuropathy regards carpal tunnel syndrome, and rating physicians should provide references in their reports to justify their position. Rating visual problems usually requires attention to the medical records to document preinjury visual status. The AMA Guides, Fifth and Sixth Editions, do not use age-adjusted corrections in assessing age-related diminished hearing, but local jurisdictions and circumstances may apply apportionment. In apportioning impairment due to aging, the examiner must understand both the science and the specific legal processes involved.