Delirium is a common complication in hospitalized patients and is often associated with significant morbidity. It is important to recognize this syndrome early so that potential causes can be identified and properly managed. Although the etiology of delirium in critically or terminally ill patients is often multifactorial, opioid analgesics are often implicated as a potential underlying cause. Certain opioids, such as meperidine, have been identified as having a greater potential for causing delirium than others. There have been no published reports of anileridine-induced delirium and an illustrative case is presented.