Thirst and drinking are essential components of normal osmoregulation in healthy man. Abnormalities of thirst appreciation, in particular hypodipsia, have profound implications for water homeostasis. The combination of cranial diabetes insipidus and hypodipsia can have particularly serious consequences, with the potential for life-threatening hyponatraemia. Although the tools for measuring thirst are subjective and lack true specificity, their use in clinical research has contributed greatly to our understanding of the physiology of thirst appreciation and the abnormal control of thirst in osmoregulatory disorders. The precise neural control of thirst appreciation remains unknown, and perhaps as a result of this, satisfactory therapies for the treatment of disorders of thirst have not yet been developed; behavioural modification and retraining of drinking habits remain the rather limited cornerstones of management.