Hyponatremia can occur at any age, but it is especially prevalent among the elderly, particularly those in acute care hospitals and long-term care facilities. The increased incidence in these patient groups is attributable to age-related impairment of fluid and electrolyte balance, use of multiple drugs that can precipitate hyponatremia, and increased vulnerability to diseases associated with hyponatremia. Recent evidence suggests that even mild chronic hyponatremia can have serious consequences in the elderly. Many current treatments for hyponatremia are limited by poor compliance, inconsistent or delayed response, or risk of adverse effects. Arginine vasopressin (AVP) receptor antagonists, a new class of drugs that block the binding of AVP to V2 receptors in the kidney's collecting tubules, may provide a safe and effective alternative.