The term maximum medical improvement (MMI) is important to understand because an evaluator cannot determine permanent impairment until a condition is permanent and stationary. In addition, in many jurisdictions MMI represents the date beyond which at least some benefits cease or when an impairment award is made or a pension is awarded. Before rendering an opinion, the evaluating physician should become familiar with the terminology used and the definitions in the applicable federal, state, or provincial law or insurance policy. The AMA Guides to the Evaluation of Permanent Impairment does not define MMI but does state that an impairment should not be considered “permanent” until the clinical findings, determined during a period of months, indicate that the medical condition is static and well stabilized. Certain principles are common to definitions of MMI and its synonyms. A generic definition could be: “Maximum medical improvement is when further treatment will probably not result in significant, sustained improvement in the symptoms or signs of an injury or illness, or an individual's physical or mental capacities.” The signs may be physical, radiographic, laboratory, electrodiagnostic, or other findings, and the definition implies that the condition is medically stable in the sense that further treatment probably will not result in appreciable, prolonged improvement.