Diabetes insipidus (DI) is an uncommon but important complication in the neurosurgical population. This retrospective study aimed to determine the incidence, profile and outcome of patients admitted to an 18-bedded neurosurgical intensive care unit who developed DI. The overall incidence was 3.7% (29/792 admissions). Aetiologies included subarachnoid haemorrhage (12/29), severe head injury (11/29), post-surgical excision of craniopharyngioma or pituitary adenoma (5/29) and acute haemorrhagic stroke (1/29). All patients were treated with a regime of fluid replacement, electrolyte correction, parenteral or intranasal desmopressin (DDAVP), or parenteral pitressin. Overall mortality was 72.4%. There were no deaths in the patients who underwent excision of tumours. Complications included acute pulmonary oedema, hypernatremia and hypokalaemia. The development of DI was found to be associated with impending brain death and mortality in the majority of patients with subarachnoid haemorrhage and severe head injury. However, careful diagnosis and management of DI after hypothalamo-neurohypophyseal surgery did not result in any permanent neurological sequelae.