The vasopressin-receptor antagonists have received approval for the treatment of hyponatraemia secondary to the syndrome of inappropriate antidiuretic hormone secretion (SIADH). It is therefore necessary that physicians encountering hyponatraemia focus on SIADH. Recent studies show that hyponatraemia is often poorly managed - insufficient diagnostic tests are ordered and patients are undertreated. At the same time, it has become clear that chronic hyponatraemia causes neurological symptoms such as gait disturbances and attention deficits. However, physicians often tolerate chronic hyponatraemia as if it were benign, or as if its treatment would cause significant morbidity. Therefore, physicians must reconsider the diagnostic and therapeutic approaches to hyponatraemia and SIADH. The Author 2009. Published by Oxford University Press [on behalf of ERA-EDTA].2009Oxford University PressThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2. 5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.