An endoscope was used in transsphenoidal surgery and eventually replaced the operating microscope as the tool for visualization. This study focuses on 50 patients (28 females and 22 males) with a median age of 38 years (range 14-88 years). 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. Seven patients had recurrent pituitary adenomas and 25 had hormone-secreting adenomas (eight patients with Cushing's disease and 17 patients with prolactinomas). Among the eight patients with Cushing's disease, seven had resolution of hypercortisolism clinically and chemically. Of the 17 patients with prolactinomas, 10 improved clinically with normal serum prolactin levels, four improved clinically with elevated serum prolactin levels, and three had residual tumors in the cavernous sinus. Among the 19 patients with nonsecreting adenomas, 16 underwent total resection and three subtotal resection leaving 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.