HYPERALGESIAMEANS INCREASED sensitivity to pain. Opioid-induced hyperalgesia (OIH) is a paradoxical situation in which increasing doses of opioid result in increasing sensitivity to pain. OIH has been identified as a clinical reality, but the incidence of clinically significant OIH is unknown. It appears to be a relatively rare but serious consequence of opioid administration. Some researchers postulate that the incidence of OIH may be much greater, as the large number of patients with persistent noncancer pain who fail to get relief from opioids or discontinue opioid therapy because of ineffectiveness may actually have undiagnosed OIH. Currently, it is not possible to predict who will develop OIH as a result of opioid exposure.