More than 50 patients who underwent intranasal or radical (Caldwell-Luc) antrostomy for chronic recurring sinusitis and who had still the same symptoms as before the operation, were examined by endoscopy and polytomography/CT. More than 50% still had polypoid changes of the maxillary sinus mucosa. No correlation was found between the degree of the patient's symptoms and the degree of the maxillary sinus pathology or the patency of the naso-antral window. CT demonstrated anterior ethmoid disease in all of the patients, correlating well with the endoscopic findings and the patient's symptoms. This again proves that the anterior ethmoid holds the key position for re-infection or cure of the larger dependent sinuses. Functional endoscopic sinus surgery therefore aims at the primary infective foci in the anterior ethmoid and usually cures disease in the larger sinuses without an attack upon the latter sinuses.