Traumatic brain injury (TBI) usually is described in terms of the severity of the initial neurologic insult and is defined by the Glasgow Coma Scale (GCS) score; the presence and duration of amnesia (retrograde and anterograde); and the presence and duration of alteration in or loss of consciousness. According to the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), the evaluating physician should consider the following: narrative history; most recent clinical evaluation; assessment of current clinical status; plans for future treatment; diagnosis and clinical impressions; and estimated time for full or partial recovery. Individuals who present with brain disease or damage also may experience impairments in several parts of the body or nervous system. Physicians who evaluate TBI must be familiar with numerous relevant sections in Chapter 13, The Central and Peripheral Nervous System, as shown in a table in the article. Individual impairments can be combined using the Combined Values Chart in the AMA Guides. Also, the AMA Guides requires the examiner to grade mental status impairment based on the individual's ability to perform activities of daily living and may require neuropsychological testing. The evaluation of TBI impairment and disability is by no means a simple undertaking for any clinician, and evaluators must familiarize themselves with disability and impairment evaluation protocols and their limitations.