Fluid and electrolyte disturbances are a common feature of heart failure. Among the electrolyte disturbances that occur in heart failure, disorders of potassium and magnesium have traditionally received the most attention. Abnormalities involving either of these actions serve as risk factors for sudden cardiac death/arrhythmias. More recently, a growing appreciation has emerged for the importance of hyponatremia in the heart failure patient. Hyponatremia is multifactorial in origin, and its presence correlates with disease severity and outcome. There are few effective therapies for hyponatremia, and those that are available are not viewed as offering specific survival benefits per se. The recent availability of vasopressin receptor antagonists, however, offers a different approach to the management of this complex electrolyte disturbance, but one that is still evolving as to the scope of its clinical benefits.