Because of their education and training, treating physicians often address causality only in terms of differential diagnosis (ie, what is causing the individual's symptoms and signs). Etiology also can be considered from a prophylactic or therapeutic standpoint (ie, how to prevent recurrent injury or eliminate the cause of an illness). In workers’ compensation, causation analysis extends beyond diagnosis, prophylaxis, and treatment and must consider whether the condition is attributable to the workplace. The terms cause, effect, exacerbation, and aggravation have specific meanings in the AMA Guides to the Evaluation of Permanent Impairment and are defined, with discussion. Three criteria must be met before causation is established in workers’ compensation: the cause is medically probable; the effect is medically probable; and the cause and effect probably are etiologically related (ie, the occupational trauma likely caused the injury, or the exposure caused the illness). A table presents the steps in a causation analysis in workers’ compensation: 1) define the injury, activity, or exposure (cause); 2) establish the diagnosis; 3) determine generic causation; specifically, determine if the reported mechanism, activity, or exposure ever causes the patient injury or disease; 4) determine specific causation in this instance and determine if another (more probably) nonoccupational cause was involved.