The incidence and duration of delirium is probably the best measurement of the quality of acute hospital care of old people. A patient with delirium is always seen as a diagnostic challenge to the geriatric team since the only effective treatment is to prevent, detect and treat the underlying causes of delirium. Predisposing and precipitating factors has to be dealt with simultaneously and the best conditions for the recovery of the brain have to be created. New threats to the brain have to be prevented and harmful medication should be avoided. Long-term follow-up of the patient with delirium is necessary since delirium can be the first symptom of a preclinical dementia.