Abstract: Experimental stapedectomy was carried out in cats. The results are: I. Vein graft, fascia or fat tissue sealed the oval window fairly well, with watertight closure, good elasticity, little scar formation and slight foreign body reaction. Among these tissues used, the fat plug seemed to be the most useful material for sealing. 2. In some cats’ears, stapedectomy was undertaken without subsequent coverings. It was found that in one of these ears the oval window was sealed by the mucoperiosteum of the tympanum and the endosteum of the vestibule in the form of a thin membrane of two distinct layers. If grafts were used, these two layers of tissue could still be found with the graft lying in between them. 3. In case fragile pieces of the footplate or other foreign bodies inadvertently fall into the vestibule, removal from the vestibule with the use of hooks should be condemned in order to avoid trauma to the cochlea. 4. It is exceedingly important to prevent the formation of the perilymph fistula in order to avoid inner ear infection. Two ears had been found to be invaded by purulent labyrinthilitis which was due to the presence of fistulas around the window.