In delirium, there is an acute change of consciousness with fluctuations in attention, cognition and perception. Delirium can be provoked by medical conditions, or the use or withdrawal of drugs. Risk factors include older age and cognitive impairment. Delirium is associated with many complications, represents a significant emotional burden for the patient and caretakers, increases length of stay in the hospital, and causes higher health care costs. Non-pharmacological measurements can sometimes prevent delirium, and are essential for its treatment with proven effectiveness. Antipsychotics should be administered only as an exception, not as a rule. Antipsychotics may be of use when the patient puts himself or others in danger, or when he suffers substantially from hallucinations.