The pterygo-maxillary fossa, hidden behind the face under the base os the present time. The scanner has transformed the investigation of this region and offers the possibility of discovery of processes limited to the pterygo-maxillary fossa which was above all known as an area affected by the extension of tumour processes arising in the maxillary sinus of parotid. A topographical division of the pterygo-maxillary fossa is suggested on the basis of CT pictures and surgical approaches. The region of the pterygoids may be easily reached via a transmandibular, the technique of which is described.