OBJECTIVE: Clinical features of pituitary hemorrhage vary from asymptomatic to catastrophic. The purpose of this study was to evaluate the factors related to severity of hemorrhage of pituitary adenoma. METHODS: Pituitary hemorrhage was noted in 32 of 88 patients who underwent operations between January 2000 and December 2007. Clinical status was classified into group I (no hemorrhage symptoms), II (mild to moderate symptoms without neurological deficit), and III (with neurological deficit), and was compared to radiological, pathological, and operative findings. All patients were operated by transsphenoidal approach, and hemorrhage-related symptoms were relieved. RESULTS: Groups I, II, and III comprised 15, 10 and 7 patients, respectively. In group I, hemorrhage volume was under 1 mL in 11 (73.3%), but, it was above 1 mL in 7 (70%) of group II and in all cases of group III. Hemorrhage stage based on MRI findings was chronic or subacute in 11 (73.3%) of group I, acute in 6 (60%) of group II, and acute or hyperacute in 6 (85.7%) of group III. Pathological examination revealed chronic-stage hematomas in 5 (50%) group II patients. Functioning adenomas were found in 5 (33.3%) group I patients but none in group II or III patients. Silent adenomas were found in 4 (26.7%), 8 (80%), and 3 (42.9%) in groups I, II, and III, respectively. CONCLUSION: Clinical features of pituitary hemorrhage may differ with the radiological and immunohistopathlogical findings. Persistent symptoms are related to the chronic stage of hematoma requiring surgery for symptom relief. Neurological deficits are caused by large amount of acute hemorrhage requiring emergency operation. Silent adenoma is related to the severity of pituitary hemorrhage.