The duration of opioid therapy after surgery is the strongest known predictor of ultimate misuse, and researchers have reported that the number of days for which medication was prescribed and the total number of postoperative prescriptions each predicts long-term use. This article addresses the question of rating the impairment for an individual with no history of substance use disorder before a work injury, who is prescribed opioids for this injury, and who subsequently develops opioid use disorder (OUD). The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, should be used in conjunction with the AMA Guides to the Evaluation of Permanent Impairment, (AMA Guides), Sixth Edition. A person who is prescribed opioids is not yet at maximum medical improvement (MMI) and cannot be rated. Referral for substantiation of the diagnosis and for initiation of treatment are necessary before OUD is confirmed and the patient is at MMI. The AMA Guides is based on impairments of activities of daily living (ADL), so a patient's MMI should result in a happy outcome and no impairment, although the burden of treatment compliance may be a relevant consideration. The article concludes with an extensive literature review, including abstracts of published articles regarding OUD in various settings.