43 cases of large labyrinthic fistulas caused by a cholesteatoma of the middle ear were studied (33 External Semi-circular Canal fistulas, 4 External Semi-circular Canal amputations with opening of the vestibule, 3 of the promontory, 2 of the oval window, 1 of the Semi-circular Canal). The audiometric, preoperative, radiological data was analyzed. The radiological exam is often disappointing for the average-sized fistulas. Preoperative labyrinthization is moderate for External Semi-circular Canal fistulas and even for certain vestibular amputations; it is often incomplete in the other locations. Systematic exeresis of the cholesteatoma matrix is recommended by the authors, at least for the External Semi-circular Canal fistulas as it is not generally accompanied by aggravation of the bony curve. In the other locations, surprising auditory preservations were observed. In conclusion, the presence of External Semi-circular Canal fistulas should not be a counter-indication for carrying out a ossiculoplasty.