Delirium is a common neuropsychiatric complication to acute physical illness in older, hospitalized patients. It is associated with a poor outcome. The pathophysiogenesis is unknown. The neurochemical and neuroinflammatory hypotheses are supported increasingly. Short-term, low-dose haloperidole is still the best choice of treatment in controlling symptoms in hyperactive delirium, but atypical antipsychotics are probably equally efficacious. Antipsychotics also appear to have a beneficial role in hypoactive delirium, but the evidence is weak. There is a weak evidence of effect of prophylactic, non-pharmacological interventions.