The authors identified the added cost attributable to postoperative delirium in patients undergoing elective surgery. The authors evaluated patients (n = 500) before their elective surgery, assessing cognitive functioning, medical conditions, medication usage, and other information regarding their health status. Using DSM-IV criteria, the authors assessed patients for delirium on Postoperative Days 1-4. Medical record review provided laboratory, radiological, and pharmaceutical information. The authors analyzed length of stay (LOS), comprehensive cost data collected through the hospital, and a group practice financial database to determine differences among those developing delirium. Of the 500 patients assessed, 57 (11.4%) developed delirium during the study. Delirium is an extremely costly disorder, both to the patient in terms of morbidity and mortality and to the medical facility. A prolonged LOS increases charges to third party payors and reduces return to physicians and hospitals when delirium develops. Careful presurgical screening and targeted postoperative interventions may help contain LOS and costs while affording greater physical, emotional, and cognitive health to patients hospitalized for elective surgery.