This is an analysis of 1,024 primary cases of mastoid surgery for cholesteatoma operated upon during a ten-year period at the Otologic Medical Group, Inc. Our philosophy of management of the mastoid in these cases has been as follows: 1) avoid an open mastoid cavity when possible; 2) perform the operation in two stages if necessary; 3) reexplore the mastoid and middle ear for residual cholesteatoma when indicated. One-third of 380 revised cases had residual cholesteatoma, disease left by the surgeon. In 260 cases in which the surgeon felt it unlikely that there was residual disease he found it in 23%. In 4% this residual cholesteatoma was found in the mastoid. The incidence of residual cholesteatoma was higher in children and in planned, as opposed to unplanned, revisions. Residual cholesteatoma was detected in the middle ear more frequently than in the epitympanum, and in the epitympanum more frequently than the mastoid. Indications for, and timing of, the reexploration are discussed. Recurrent cholesteatoma refers to a retraction pocket and must be differentiated from residual cholesteatoma; the causes, prevention and treatment are different. Recurrent cholesteatoma was detected in 5%. The most common complication of the disease was a labyrinthine fistula (10%). Operative facial nerve damage occurred in one case. The most common postoperative complication was graft failure (3%). Intact canal wall tympanoplasty with mastoidectomy should be performed as a two-stage procedure in most cases when used in the treatment of aural cholesteatoma.