Oto-endoscopes allow surgeons to control blind pockets within the middle ear. Many surgeons credit the reduction of residual cholesteatoma in their practice to the use of oto-endoscopes. Since 1988, the author has been using rigid endoscopes in combination with the operating microscope in cholesteatoma surgery. Between 1988 and 1999, 231 primary cholesteatoma operations were performed. The operations included closed cavity mastoidectomy (53 patients), small cavity mastoidectomy (115 patients), open mastoidectomy with primary canal wall reconstruction (44 patients) or mastoid obliteration (19 patients). The median follow-up period was 6.5 years. The incidence of residual cholesteatoma is closed cavity mastoidectomy (9.4 per cent) was found to be similar to that of open cavity mastoidectomy (8.7 per cent). Site analysis of the residual cholesteatoma revealed an incidence of 3.6 per cent in the epitympanum, 10.5 per cent in the sinus tympani and 0.7 per cent in the mastoid bowl. This study showed that residual cholesteatoma has not been eliminated with the use of middle-ear endoscopy, although the incidence has reduced the figures for closed cavity mastoidectomy to single figures.