The modified Lynch operation (Neel-Lake) differs in several ways from the operation described by Lynch. The operation begins with an intranasal anterior ethmoidectomy. The agger nasi cells are removed by curetting forward between the frontal process of the maxilla and the septum. The middle turbinate, normal-appearing mucosa of the frontal-ethmoid complex, and frontal process of the superior maxilla are preserved. Bone removal is limited in most cases to the anterior floor of the frontal sinus, a portion of the lacrimal bone, and the bone over the anterior ethmoid cells. Another important difference is the use of soft, nonreactive material (thin Silastic sheeting) to stent the nasal-frontal passageway. Removal of all the mucosa of the frontal-ethmoid-sphenoid complex is unnecessary for a good postoperative result, and the remaining normal mucosa hastens the process of reepithelialization of the nasal-frontal duct. The patients in our original study group have been observed for a period of 5 to 20 years (mean, 13.5 years) after the surgical procedure. This is the longest period of follow-up for any group of patients reported in the literature. The incidence of failures increased from 7% (one duct) to 20% (3 of 15 ducts) after an additional 7 years of follow-up.