Delirium is an acute, potentially life-threatening organ dysfunction with an incidence reported to range between 10 and 92 %. Delirium is potentially preventable and has a great impact on patients' outcomes, even beyond their stay in the hospital. It was found to be associated with persisting cognitive deficits, increased physical dependence, institutionalization, and increased mortality. Delirium is the result of the complex interplay of predisposing and hospital-associated precipitating risk factors, some of which are potentially preventable and modifiable.Delirium is frequently not or incorrectly diagnosed. Subtype, severity, and duration are associated with prognosis. Both prevention and treatment necessitate implementation of daily structured delirium screening. Prevention requires risk assessment: predisposing and precipitating factors should be recognized and treated, if modifiable. Prevention and treatment options include behavioral, cognitive training programs and possibly anti-inflammatory and antipsychotic drugs. Delirium requires search for underlying illness, intoxication or drug side effects.This review summarizes recent work from the last two years, giving a brief overview and background information with regard to risk factors, impact on outcome parameters, mechanisms of pathophysiology, non-pharmacological and pharmacological prevention and treatment strategies of delirium in critically ill patients.