Delirium is a neuropsychiatric sindrome characterized by acute onset, a fluctuating course, an altered level of consciousness, disturbances in orientation, memory, attention, thinking, perception and behaviour. One third of patients aged 70 or older were admitted to the general medical service of an acute care hospital experience delirium. The development of delirium is associated with worse outcome increased a 10-fold risk for death and a 3-to 5-fold risk for nosocomial complications, prolonged length of stay, and greater need for nursing home placement after discharge. Therefore patients with delirium have higher morbidity and mortality rates, higher re-admission rates, and a greater risk of long term institutionalization care, thereby having a significant impact on both health and social care expenditure. The cost of delirium to the health-care system is then substantial. Despite its clinical importance and health-related costs, it often remains under-recognized and inadequately managed. Recent evidence suggests that a better understanding and knowledge of delirium among health care professionals can lead to early detection, the reduction of modifiable risk factors, and better management of the condition in the acute phase.