The use of opioid medications for analgesia is associated with concerns about adverse side effects and the potential for development of physical dependence, tolerance, or addiction. Pain often is undertreated, which may provoke drug-seeking behavior by patients. Physicians must assess requests for more pain medication as stemming from either undertreatment of pain, development of physical tolerance, or addiction. Important tools for addiction screening include the use of questionnaires, patient interviews, and lab tests. In this study, the physiological and behavioral consequences of chronic pain and its treatment with opioids, along with guidelines for prescribing opioid pain medication, are presented.