Hyponatremia is prevalent in hospitalized patients and predicts a poor prognosis. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is perceived as one of the most frequent causes of hyponatremia. Traditionally, chronic hyponatremia has been treated with fluid restriction and demeclocycline. However, these treatment options have been unsatisfactory due to problems with treatment compliance and/or safety concerns. In recent years, several vasopressin-receptor antagonists, the vaptans, were introduced into clinical practice. One of these vaptans - tolvaptan - is an oral vasopressin V2-receptor antagonist that induces free water excretion without increasing sodium excretion. Few studies have assessed the role of vaptans in treating hyponatremia in a population with only SIADH. Current data shows that vaptans may safely correct mild or moderate hyponatremia in patients with SIADH. However, further clinical trials are needed to determine the optimal dosing, proper monitoring and adequate precautions for the use of vaptans in this patient population.