Objective: Endoscopic endonasal transsphenoidal surgery (EETS) is used mainly in pituitary adenomas, other tumors of the sellar and parasellar region, rhinorrhea surgery and optic nerve surgery. The results of 200 patients who underwent EETS in our clinic were evaluated. Material and Method: Two hundred patients who underwent EETS at Neurosurgery Clinic of Bakırköy Prof. Dr. Mazhar Osman Mental Health and Neurological Disorders Education and Research Hospital in 2014-2017 were retrospectively evaluated. Follow-up period was 3-43 (mean 15) months. 108 patients were female (54%), 92 male (46%) and mean age was 47.5 (15-79) years. Results: Pathology results showed that 119 of 120 patients had secretory pituitary adenomas including Cushing’s disease (n=23), prolactinoma (n=5), acromegaly (n=37), 12 mixed type (n=12), increased TSH levels (n=3), 29 gonadotropinoma (n=29), 47 had non- secretary adenoma (n=47). Besides cases diagnosed as meningioma (n=5), 5 craniopharyngioma (n=5), 6 cordoma (n=6), neuroendocrine tumor (n=2), germinoma (n=1), 6 Rathe cleft cyst (n=6), ossifying fibroma (n=1), spontaneous rhinorrhea (n=7), and abscess (n=1) were detected. Epistaxis was found in 15, transient diabetes insipidus (DI) in 14, CSF leakage in 23, permanent anosmia in 5, temporary visual loss in 1, and late period sinusitis in 7 patients. No major vascular injury was found, and 2 patients died due to meningitis and its complications. Conclusion: In EETS, the incidence rates of CSF fistula were reported in 0.5-15%, epistaxis in 0.6%, transient DI in 11.99%, permanent DI in 3.41% of the cases ,while remission and total resection rates ranged between 60-80% of the cases. The frequency of epistaxis in our series was higher than that of the literature. Rates of temporary DI, remission and total resections were consistent with the literature; while permanent DI was relatively lower. We believe that EETS is an effective and reliable surgical method.