Objective: To explore the techniques and methods of endoscopic transnasal transsphenoid surgery for pituitary adenoma. Method: We treated 678 cases with pituitary adenoma by endoscopic transsphenoidal surgery between May 2000 and May 2006. All cases were operated through a transnasal transsphenoid approach between the nasal septum and middle nasal concha, first to enlarged sphenoid ostium and opened sellar floor with a high-speed drill and then removed the tumor step by step. Sixty-two percent of cases (420 cases) got 6-24 months of follow-up. Results: Among the 678 pituitary adenomas, tumor removal was total in 543 (80.1%), subtotal in 118 (17.4%) and partial in 17 (2.5%). Ninety-eight percent (643 of 655 cases) obtained an improvement in clinical symptoms at some extent after the operation. Post-operative complication (including subarachnoid hemorrhage, nasal cavity bleed, nostril infection, nasal wing deformation and cerebrospinal fluid nasal leakage) occurred in 21 patients (3%). Among the 420 follow-up patients, tumor in four cases recurred 2 years after the first operation. Conclusion: Endoscopic transsphenoidal surgery of pituitary adenomas is a valuable microinvasive neurosurgery technique of minimal invasiveness, being effective and safe, yet requiring simple manipulation. With technological and scientific advancements, endoscopic transsphenoidal surgery will improve and develop step by step.