The surgical management of various diseases of the ethmoid-sphenoid region is absolutely indicated in many cases because of the direct neighbourhood and the intimate relationship between a pathological process of these sinuses and a spreading of an infection or a tumor to the adjacent organs such as the orbit, the base of the skull, the dura, the optic nerve and the internal carotid artery. The optic nerve and the carotid artery are intimately related to the lateral wall of the sphenoid sinus and may even bulge into the cavity. In cases of an atypical posterior ethmoid cell we must expect an anomaly of the course of the optic canal with the increased danger of an injury to the optic nerve. The various possibilities of pneumatisation of the ethmoid-sphenoid region are described and illustrated. The diverse methods of the ethmoid-sphenoid operations are demonstrated and compared regarding their effectiveness and operative risk. Details of several iatrogenic injuries of the orbit, the dura or the optic nerve and the management of these lesions are mentioned. The medico-legal situation and the importance of the preoperative informed consent of the patient are discussed.