Early return to work is fundamental in the treatment of occupational injuries, but the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides) may require temporary or permanent work restrictions. The US Department of Labor Physical Demand Characteristics of work classifies jobs by exertional level (sedentary, light, medium, heavy, and very heavy). The Workplace Functional Ability Guidelines (WFAGs) consist of 21 categories of health impairment and emphasize what the worker can do, ie, the “functional ability.” Musculoskeletal symptoms and signs such as strength, range of motion, or radiographic findings are not good predictors of functional abilities, nor does standardizing the method for work-capacity determination. Measures of physical work performance, even when conducted by highly trained individuals, have low interrater reliability when used for complex tasks. Any discrepancy in expectations between the physician and worker about capabilities and anticipated progress should be resolved. This may be best done if the physician is familiar with the requirements of the job and can offer suggestions about, for example, reducing the stress on an injured body part by using a different model of a tool. Individual differences in motivation, pain tolerance, conditioning, and so on make it difficult to determine work restrictions, but physicians should attempt to return the worker to gainful employment as early as possible.