Since computerized transaxial tomography (CTT) scanning at the Mayo Clinic (1974-1981), 25 cases of metastatic diabetes insipidus (DI) have been identified. Of 100 consecutive cases of DI of any cause, 14 were due to metastatic cancer. Diabetes insipidus was the initial presentation in 11 patients with systemic cancer. In the 11 patients, the most common sources metastatic to the posterior pituitary-hypothalamic region were lung (3) and the leukemia/lymphoma group (4). Although skull x-ray results were usually normal (9 of 11), CTT scanning results were abnormal in 5 of 11, including demonstration of pituitary stalk enlargement, suprasellar masses, or both. Metastases elsewhere in the nervous system were apparent in four patients. Anterior pituitary and visual system involvement occur in a minority group of patients.