The purpose of the study is to evaluate the ability of endoscopic extended transsphenoidalapproach for treatment of gigantic pituitary adenoma. The clinical data of 13 cases with gigantic pituitary adenoma treated by endoscopic extended transsphenoidalapproach was studied retrospectively. The tumor of all patients was total resection in endoscopes. Postoperative 10 Patients received radiotherapy. In postoperative MRI examination, there was remnant of tumor in 6 patients. There were no regrowth or recurrence during 12 months postoperative. Six patients occurred transient diabetes insipidus, 2 patients with transient cerebrospinal rhinorrhoea cured by conservative therapy. One patient occurred acute hypopituitarism postoperatively. There were no death or intracranial infection and nasal complication such as nasal adherence in all patients. The extended transsphenoidalapproach can be used for treatment of gigantic pituitary tumor. The surgeon should be familiarity with the sellar and parasellar anatomy and skilled with transsphenoidal surgery.