Facial disfigurements, including those caused by burns (thermal, chemical, or electrical) or trauma, are rated in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, Chapter 11, which also discusses occupational overexposure to sunlight, airborne chemicals, heavy metals, and allergens that may lead to head and neck cancers and degraded ability to breathe, chew, swallow, smell, or speak. Additional relevant impairments include those of olfaction and taste, chewing and swallowing, voice and speech, and of the upper respiratory passages. For upper air passage defects and voice and speech impairments, the evaluator assigns an impairment rating by selecting the relevant table or grid in Chapter 11 and then assigning the appropriate impairment class, as determined by the key factor. The patient's history is the key factor for upper air passage deficits, and the performance measures of audibility, intelligibility, and functional efficiency collectively act as the key factor for voice and speech impairments. Once they select an impairment class, evaluators can modify the rating within the impairment class by considering remaining variables. When rating the patient's ability to smell and taste or chew and swallow, raters do not use impairment classes or modifiers. Rather, they assign impairment within an allowable range largely based on professional judgment complemented by objective findings and a well-documented rationale.