We evaluated water metabolism in 11 patients with hypothalamic-pituitary sarcoidosis. Seven patients had abnormal water metabolism: one had partial antidiuretic hormone (ADH) deficiency, one had severe ADH deficiency, one had severe ADH deficiency and deficient thirst, one had only deficient thirst, and three had excessive thirst. In four of the five with thirst disturbances, there was loss of congruence of osmotic thresholds for thirst and ADH release. Five of our patients presented with polyuria and polydipsia, but only two had true diabetes insipidus, whereas three had organic primary polydipsia with adequate endogenous ADH. That disordered thirst resulting in polydipsia was more common than true diabetes insipidus is at odds with previously held views on the prevalence of ADH deficiency in this condition.