Backgrounds: Diabetes insipidus(DI) is a clinical syndrome characterized by excretion of copious volumes of dilute urine combined with persistent intake of abnormally large quantities of fluid. Central DI, caused by lack of antidiuretic hormone(ADH), most often results from lesions in the hypothalamic-neurohypophyseal axis. Magnetic resonance(MR) imaging is particularly useful in documenting the presence of a structural lesion, as opposed to assigning a diagnosis of idiopathic DI for which only symptomatic therapy is prescribed. Recently, several reports have described a specific MR finding in central DI, that is absence of normal posterior pituitary bright spot(PPBS). Methods: We retrospectivesly studied the clinical and MR findings in 25 patients with central DI, diagnosed by warter deprivation test. Results: 1) The subjects included 17 males and 8 females, between the ages of 2 and 58 years. 2) 24-hour urine volumes were 2,340~13,750 mL, and mean urine osmolarity was 147.7±65.8 mOsm/kg. The 23 subjects diagnosed complete central DI by warter deprivation test. 3) We found that the most common cause of cntral DI was infiltrative lesions of hypothalmic-neurohypophyseal axis(60%). Germ cell tumor was the single leading cause in present study, accounting for 36% of cases. The other causes were found, including pituitary apoplexy, meningitis, and trauma. Idiopathic central DI accounted for 20% of all cases. 4) Growth hormone deficiency was the most common accompanying anterior pituitary deficit, and panhypopituitarism was found in 7 cases, Hyperprolactinernia was seen in 6 cases. 5) In all patients, PPBS on Tl weighted MR images were not observed. A thickened pituitary stalk was seen in 15 cases(9 patients with germ cell tumor, 3 patients with histiocytosis X, 1 patient with tuberculosis, 2 patients with unknown origin). Conclusion: In our results, the most common causes of central DI was suprasellar infiltrative lesions. MR is currently the imaging methods of choice in the evaulation of dysfunction of the hypothalamic-neurohypophyseal system in patients with central DI. A specific MR finding, that is loss of normal PPBS allows a confirmative diagnosis of central DI(J Kor Soc Endocrinol 11: 285-292, 1996).