Nasal polyposis has to be considered as an advanced form of chronic ethmoiditis requiring surgery. Its proliferation starts in the osteo-meatal complex of the lateral nasal wall, and follows typical routes. Depending on its extension endoscopical partial resections of the ethmoid may be carried out. For diffuse polyposis of all sinuses a complete endonasal ethmoidectomy together with the fenestration of the frontal, sphenoidal and maxillary sinuses (pansinus operation) is indicated. The importance of preoperative imaging by CT or polytomography, and of flanking measures, is stressed. Fair results concerning subjective relief and objective proof of lasting mucosal recovery are reported against the background of a low incidence of surgical complications.