Delirium is a common complication of acute illness in older people. Earlier and more reliable detection could be achieved by greater routine cognitive testing in older people. Research evidence suggests that episodes of delirium and duration of delirium could be reduced by about one third if systems of care that prioritized delirium risk factor amelioration were comprehensively adopted. Specialist delirium units have a place in leading and disseminating best practices. Health service regulators should consider monitoring delirium as an adverse health care outcome.