In a 30-month period, 14 cases of labyrinthine fistula were seen, and 212 mastoid operations were performed during that time for an incidence of 6.6%. In the 11 cases of fistula involving the horizontal or posterior semicircular canal, cholesteatoma matrix was left over the fistula in seven cases and removed in four cases. Preoperative bone-conduction hearing levels and discrimination scores were retained in these 11 patients. In three patients with fistulas involving the vestibule or cochlea, cholesteatoma matrix was removed. Complete deafness occurred in two of these patients. Our experience suggests that cholesteatoma matrix can be removed over most labyrinthine fistulas providing that great care is exercised. It may not be safe to remove the matrix over anterior-placed fistulas.