Delirium is one of the most important age-related diseases. Approximately 10-20 % of old people treated in hospitals are affected by delirium. Due to its unfavourable prognosis, the prevention of delirium is of growing importance. The practice-oriented book deals with the diagnostic and therapeutic approach on the basis of the most recent evidence knowledge, as well as current possibilities and guidelines for prevention. It includes sections on the history of delerium, epidemiology, the spectrum of symptoms and on etiology and pathogenesis. Case descriptions round off the work.