Severe, diffuse polyposis can be adequately treated through a transnasal approach which combines microscopic and endoscopic surgery. The operating microscope is used to perform ethmoidectomy, usually from the front to the back, and to open the sphenoid sinus and the antral window. The telescopes allow the sphenoid and maxillary sinuses to be cleaned under direct view control as well as enabling good drainage to be performed from the frontal sinuses. The results from 22 consecutive patients were good, with a very low rate of minor post-operative complications.