Normal human water intake spans a large range owing to the body’s ability to excrete large volumes of water in times of excess and conserve in times of scarcity. Recently, chronic intakes of either large volumes (HIGH) or small volumes (LOW) of water have been investigated. Adaptations within the renal regulation of water through the secretion and reabsorptive actions of the hormone arginine vasopressin and the thirst mechanism have been observed to differentiate these 2 groups during normal living. Increases or decreases in daily fluid intake in LOW and HIGH resulted in appropriate arginine vasopressin and perception of thirst changes, which enabled fluid balance in both of these populations. However, future research should establish if the chronic adaptive mechanisms, by which fluid is regulated have long-term negative outcomes.