Illness behavior refers to the ways in which given symptoms may be perceived, evaluated, and acted on by different persons and can be conscious or unconscious (the latter means unnoticeable and refers to mental processes and content that are significant in determining behavior but of which the person is unaware). Further, consciousness of actions (voluntariness) and consciousness of motives (intentionality) are not necessarily associated. Illness behavior can be learned and reinforced and is a potential confounder in the association between illness or injury and impairment or disability. Illness behavior is not an impairing condition according to the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), and a table in the article describes the characteristics of the symptom magnification syndrome and other related conditions. Three diagnoses—somatic symptom disorders, illness anxiety disorder, and conversion disorder—possibly are ratable using the AMA Guides. Unsupported and insupportable conclusions regarding symptom exaggeration represent substandard practice because of the importance of such conclusions to the disposition of patients who present for assessment of impairment or disability. Similarly, failure to note and account for illness behavior and symptom exaggeration also represent substandard practice because the goal in impairment ratings is to note and account for all evidence related to the impairment, including the extent of illness behaviors.