Symptomatic cerebral vasospasm (CVS) after transsphenoidal surgery (TSS) is very rare compared with vasospasm resulting from aneurysmal subarachnoid hemorrhage (SAH). Fewer than six cases documented by cerebral angiography have been reported. We evaluated the records of 15 patients in whom SAH developed after TSS. Their clinical symptoms, radiological and laboratory findings were analyzed. Among 15 patients with postoperative SAH, 11 did not show CVS during their postoperative course. However, four patients presented with various clinical symptoms suggestive of CVS on postoperative days 7-9. They showed an abrupt drop of serum sodium level 1 or 2 days before the onset of CVS symptoms. Patients with TSS-related SAH should be managed with proactive and aggressive treatment. Hyponatremia, which usually occurs around the first week after TSS, should not be ignored as a matter of metabolic or hormonal disequilibrium commonly encountered after pituitary surgery.