Endoscopic endonasal transsphenoidal approach (EETA) is an effective and relatively safe to remove pituitary adenomas and other sellar region tumors. One of the most serious complications of transsphenoidal surgery is damage to the cavernous segment of the internal carotid artery, which by different authors occurs at 0 to 3.8%. In the period from 2005 to March 2013 in Burdenko neurosurgical institute 3,000 patients with pituitary adenomas were operated by standard endoscopic transsphenoidal approach. Damage to the internal carotid artery (ICA) occurred in 4 patients, which amounted to 0.13%. To all patients with damage of the ICA angiography was performed in which identified one case of occlusion of the ICA and three cases of false aneurysm formation. Three patients underwent endovascular treatment. Damage to the internal carotid artery may be associated with the wrong orientation in the surgical wound, or excessively aggressive manipulations in the cavernous sinus. Damage to the cavernous segment of the ICA during transsphenoidal surgery is a rare but potentially fatal complication. Extremely important is the correct localization of the middle line and ICA using navigation systems and Doppler ultrasound.