There are 2 subtypes of delirium based on altered psychomotor activity. The hypoactive subtype is characterized by psychomotor retardation, patient drowsiness, and reduced arousal. The hyperactivity subtype is often overly alert and agitated, with prominent autonomic hyperactivity. In addition, the hyperactive subtype most often presents with delusions and perceptual disturbances such as hallucinations. About half of the patients with delirium have a mixed type, with components of both subtypes or fluctuating between them. Only about 15% of patients are strictly hyperactive. Those who are young, have the overactive subtype and have an etiology related to substance abuse have a shorter hospital stay and a better prognosis. The prognosis is good in most cases if the causative factors can be corrected. The average duration of delirium ranges from a few days to 2 weeks, and is longer in the elderly. Older patients may not recover to their original level. Approximately 1/3 of delirium is followed by a form of partial delirium in the elderly that meets some but not all of the criteria, and less than 20% of patients return to their original level after 6 months. In addition, following delirium, elderly patients often have decreased ability to live and home care may be increased. Delirium is associated with increased mortality, but is due to underlying dementia, advanced age, and disease severity. Children may also have residual deficits with decompensated or persistent mild perceptual-motor abnormalities and learning difficulties. In general, the prognosis should be improved by increasing the awareness of delirium, diagnosing the causative factors as soon as possible and managing them well and comprehensively.