Delirium is a common acute neuropsychiatric syndrome. It is characterized by concurrent disturbances of consciousness and attention, perception, reasoning, memory, emotionality, the sleep-wake cycle as well as psychomotor symptoms. Delirium caused by alcohol or medication withdrawal is not the subject of the current review. Specific predisposing and precipitating factors have been identified in delirium which converge in a common final pathway of global brain dysfunction. The major predisposing factors are older age, cognitive impairment or dementia, sensory deficits, multimorbidity and polypharmacy. Delirium is always caused by one or more underlying pathologies which need to be identified. In neurology both primary triggers of delirium, such as stroke or epileptic seizures and also secondary triggers, such as metabolic factors or medication side effects play a major role. Nonpharmacological interventions are important in the prevention of delirium and lead to an improvement in prognosis. Delirium is associated with increased mortality and in the long term the development of cognitive deficits and functional impairment.