Body fluid regulation is pivotal to human health and is served by extensive clinical and pre-clinical science. By combining modern advances with previous findings in the field, this book presents a comprehensive treatment of major experiments, theories, and new advances in the field of body fluid regulation, thirst, and drinking. It features the main integrative brain mechanisms for fluid regulation, the development of such systems, fluid balance during heat and exercise, aging and clinical disorders, and comparative aspects of fluid regulation. The volume focuses on mammalian thirst or drinking behaviour alongside relevant aspects of the physiology of fluid balance. The principal fluid compartments and their regulation by both intakes and losses are highlighted, using both human and animal studies to illustrate the main concepts.