Delirium is a complex neuropsychiatric syndrome presenting primarily with disturbances of cognition, perception and sensorium, alertness, sleep/wake cycle, and psychomotor behavior in the context of a medical etiology. The presentation can be quite variable among patients and even within a given patient because of its waxing and waning course. This variability and overlap with other psychiatric syndromes has led to substantial underrecognition and undertreatment in clinical settings. Considering the significant morbidity and mortality associated with delirium and its tremendous economic burden, the failure to diagnose, refer, and treat such patients represents a critically important public health care issue. Clinicians should be systematically educated about delirium symptoms. Also, caregivers and family members of medically compromised patients should be educated about recognizing delirium. The use of structured diagnostic instruments and scales to follow the severity of symptoms has been an improvement in the field. However, much more research is needed into the use of such instruments and how they can be applied to clinical situations to improve the detection and treatment of delirium. Similarly, research is warranted that focuses on preventing delirium, potentially by identifying susceptible patients and intervening early. It is particularly challenging to devise cost-effective interventions for preventing and identifying delirium early in its course, given the rapid pace and resource limitations in inpatient and intensive care settings, and current data do not clearly indicate that such systems have proven benefit. Still, the indisputable health and financial costs of delirium indicate that prevention and identification should be a high priority.