Hyponatremia in congestive heart failure (CHF) is associated with increased morbidity and mortality, underlining the importance of adequate assessment and treatment of this electrolyte imbalance in patients with CHF. Current treatment options for hyponatremia in CHF include hypertonic saline solution, loop diuretics, fluid restriction, and other pharmacologic agents, such as demeclocycline, lithium carbonate, and urea. Hypertonic saline solution must be administered with extreme caution because excessively slow or rapid sodium correction can lead to severe neurologic adverse effects. Loop diuretics are useful for reducing the water retention caused by CHF. However, the potent diuresis induced by agents such as furosemide results in loss of sodium and other essential electrolytes, which may exacerbate hyponatremia. Fluid restriction is only moderately effective and often difficult to implement in the hospital setting. Agents such as demeclocycline and lithium have potentially serious renal and cardiovascular side effects. The arginine vasopressin (AVP) receptor antagonists are a promising new class of aquaretic agents that increase free-water excretion while maintaining levels of sodium and other essential electrolytes. Tolvaptan (OPC-41061), lixivaptan (VPA-985), and conivaptan (YM-087) are currently under development for the treatment of hyponatremia. Although tolvaptan and lixivaptan are selective for the vasopressin-2 (V 2) receptor responsible for the antidiuretic actions of AVP, conivaptan demonstrates activity at both the V2 receptor and the V1a receptor responsible for the vasoconstricting properties of AVP. This dual receptor activity may be particularly useful in patients with CHF. These patients may benefit from the increased cardiac output, reduced total peripheral resistance, and reduced mean arterial blood pressure that results from V1a receptor blockade as well as the reduced congestion, reduced cardiac preload, and increased sodium concentrations induced by V2 receptor antagonism.