Findley first proposed the presence of age-related dysfunction of the hypothalamic-neurohypophyseal-renal axis more than 50 years ago. His hypothesis was based on clinical observations and occurred well in advance of the first assays for arginine vasopressin. Since then, the evolution of more sophisticated scientific methodologies has resulted in a corroboration of Findley's suspicion and has revealed many aspects of the physiology that underlies this manifestation of the aging process. It is now clear that many perturbations in water homeostasis occur commonly with aging. This article summarizes the distinct points along the hypothalamic-neurohypophyseal-renal axis where these changes have been characterized.