Hyponatraemia is frequent in older people and induces marked motor and cognitive dysfunction, even in patients deemed ‘asymptomatic’. Nutritional status is worse than in euvolaemic-matched controls, and the risk of fracture is increased following incidental falls. Yet hyponatraemia is undertreated, in spite of the fact that its correction is accompanied by a clear improvement in symptoms. Both evaluation of neurological symptoms and classification by volaemia are essential for a correct diagnosis and treatment of the hyponatraemic elderly patient. The syndrome of inappropriate anti-diuretic hormone secretion (SIADH) is the most common cause of hyponatraemia in older people. Nutritional status and chronicity of SIADH should be taken into account when deciding therapy. We propose an 8-step approach to the management of the elderly patient with hyponatraemia.