Endoscopic transethmoidal.transsphenoidal surgery was performed on 30 patients with pituitary tumors, and the usefulness of this procedure was evaluated. As with conventional endoscopic intranasal surgery, the ethmoidal sinuses were opened and a broad window was created in the ethmoidal sinus from the directions of the middle meatus and the olfactory cleft. Then an endoscopic washing device was attached to a 0 degree or 30 degrees rigid endoscope and it was immobilized in the left nasal cavity with an endoscope immobilization apparatus. Removal of the tumor was then started from the right side by a bimanual technique. Based on the results, this surgical procedure was judged to be useful for the following reasons (1) it makes it easy to carry out the operative manipulations even in a narrowed nasal cavity, thereby reducing the overall time required for surgery, and (2) it is possible to prevent postoperative deformities of the nasal cavity morphology caused by pressure on its lateral wall. In additional, (3) the surgical wound can be observed, and CSF leakage can be repaired immediately after completion of the operation. Corrective surgery can be performed on an outpatient basis early after the initial operation to correct postoperative deformities of the nasal paranasal cavities, which might later cause nasal obstruction or an olfactory disturbance. Finally, (4) employing the route of endoscopic transethmoidal.transsphenoidal surgery facilitates the performance of a second operation soon, or even several months, after the first operation. A second operation may be necessary in the event of recurrence of the pituitary tumor or complication by chronic sinusitis. On the basis of our experience in the this study, we conclude that our method of endoscopic transethmoidal.transsphenoidal surgery will be useful for reducing invasiveness in the nasal cavities and achieving maximum prevention of postoperative complications. In order to fulfill its potential, neurosurgeons will need to master forceps techniques in the visual field provided by the endoscope and to cooperate with otorhinologists who are skilled in endoscopic techniques.