THE DIRECT ENDONASAL transsphenoidal approach to the sella with the operating microscope was initially described more than 20 years ago. Herein, we describe the technique, its evolution, and lessons learned over a 10-year period for treating pituitary adenomas and other parasellar pathology. From July 1998 to January 2008, 812 patients underwent a total of 881 operations for a pituitary adenoma (n = 605), Rathke's cleft cyst (n = 59), craniopharyngioma (n = 26), parasellar meningioma (n = 23), chordoma (n = 18), or other pathological condition (n = 81). Of these, 118 operations (13%) included an extended approach to the suprasellar, infrasellar/clival, or cavernous sinus regions. Endoscopic assistance was used in 163 cases (19%) overall, including 36% of the last 200 cases in the series and 18 (72%) of the last 25 extended endonasal cases. Surgical complications included 19 postoperative cerebrospinal fluid leaks (2%), 6 postoperative hematomas (0.7%), 4 carotid artery injuries (0.4%), 4 new permanent neurological deficits (0.4%), 3 cases of bacterial meningitis (0.3%), and 2 deaths (0.2%). The overall complication rate was higher in the first 500 cases in the series and in extended approach cases. Major technical modifications over the 10-year period included increased use of shorter (60-70 mm) endonasal speculums for greater instrument maneuverability and visualization, the micro-Doppler probe for cavernous carotid artery localization, endoscopy for more panoramic visualization, and a graded cerebrospinal fluid leak repair protocol. These changes appear to have collectively and incrementally made the approach safer and more effective. In summary, the endonasal approach provides a minimally invasive route for removal of pituitary adenomas and other parasellar tumors.