An endoscope was used in transsphenoidal surgery and eventually replaced the operating microscope as a tool for visualization. Initially four patients underwent operation via a sublabial transseptal approach using a rigid endoscope in conjunction with an operating microscope. The 48 subsequent operations were performed through a nostril using only rigid endoscopes. Forty-four patients had pituitary adenomas and six had various other lesions. Thirteen patients had microadenomas, 16 had intrasellar macroadenomas, nine had macroadenomas with suprasellar extension, and six had invasive macroadenomas involving the cavernous sinus. Among eight patients with Cushing's disease, seven were cured. Of 17 patients with prolactinomas, 10 were cured clinically and chemically. Among 19 patients with nonsecreting adenomas, 16 underwent total resection and three subtotal resection, with residual tumor in the cavernous sinus. Postoperatively all patients who had undergone endonasal endoscopic surgery had unobstructed nasal airways with minimal discomfort. More than half of the patients required only an overnight hospitalization.