A new, simple and inexpensive technique of endoscopy of the maxillary sinus is presented. With this technique the expensive modern optical systems for maxillary antrum endoscopy are replaced by a common otoscope and a trocar specially designed to fit into the lumen of the otoscope. They are introduced into the maxillary sinus through the canine fossa. After the removal of the trocar the otoscope remains in the sinus and endoscopy of all the maxillary sinus can be performed very easily and quickly.