The author's series of 168 consecutive cases of chronic otitis media from the years 1965 to 1972 were reviewed with regard to the occurrence and management of pathological fistulae in the bony labyrinth. Fourteen cases (incidence 8.3%), of which nine involved only the semicircular canals and five involved primarily the cochlear wall occasionally associated with a semicircular canal fistula, were examined particularly in terms of postoperative sensorineural hearing loss following removal of cholesteatoma matrix from the fistula. The results indicated that the matrix can be removed with reasonable safety from most small semicircular canal fistulae. Only when the cholesteatoma matrix is firmly adherent to a large area of membranous semicircular canal is removal not recommended. When the cholesteatoma was removed from three cochlear fistulae, sensorineural hearing loss resulted. In two cases with cochlear fistula, hearing was preserved when the cholesteatoma matrix was not removed from the fistulized area. These results have been used to formulate guidelines for the surgical management of pathological fistulae of the bony labyrinth.