Objective To analyze the etiology and clinical feature of pi t uitary apoplexy.Methods The clinical data from 18 cases of pitui tary apoplexy were analyzed retrospectively.Results Main symptom s were headache in 12 cases and decreased visual acuity in 12 cases.Positive si ghs were temporal hemianopisia in 6 cases,unequal pupil in 3 cases,oculomotor ne rve(Ⅲ) paralysis in 2 cases and abducent nerve (Ⅵ) paralysis in 2 cases.Imagin g examinations showed CT positive finding in 4 cases and MRI positive finding in 6 cases.Tumor diameter was longer than 2 cm in 13 cases and less than 2 cm in 5 cases.Chromophobe pituitary tumor was found in 11 cases.All cases received surg ical operation.Conclusion Clinical features of pituitary tumor a poplexy are atypical,of which headache and visual acuity decrease are the main s ymptoms.Most cases occur suddenly or primary symptoms are deteriorated suddenly. CT and MRI positive findings are helpful for diagnosis.