Confusion in the elderly, ie, delirium, is an organic mental disorder often associated with severe somatic disease. Approximately 20-60 per cent of elderly in-patients are afflicted with transient confusion states during hospitalisation, and in more than 50 per cent of cases this escapes the notice of the attending physician. The disorder is characterised by a remarkably poor prognosis; even among those whose confusion state is transient, 20-30 per cent die before discharge, and approximately one third remain hospitalised. The occurrence of confusion in the elderly patient should alert the physician to the need of investigation to detect underlying severe disease without delay. Despite the otherwise poor prognosis, improved diagnosis and treatment should not only yield better results but also economic gain to the community.