Hyponatraemia is the commonest electrolyte abnormality, and syndrome of inappropriate antidiuretic hormone (SIADH) is the most frequent underlying pathophysiology. Hyponatraemia is associated with significant morbidity and mortality, and as such appropriate treatment is essential. Treatment options for SIADH include fluid restriction, demeclocycline, urea, frusemide and saline infusion, all of which have their limitations. The introduction of the vasopressin-2 receptor antagonists has allowed clinicians to specifically target the underlying pathophysiology of SIADH. Initial studies have shown good efficacy and safety profiles in the treatment of mild to moderate hyponatraemia. However, studies assessing the efficacy and safety of these agents in acute severe symptomatic hyponatraemia are awaited. Furthermore, the cost of these agents at present may limit their use.