Data from the records of 251 consecutive patients with aural cholesteatoma treated surgically by one surgeon (R.E.G.) between 1962 and 1980, using mainly wide access approaches of atticotomy and attico-antrostomy, and assiduously followed up, formed the basis of an analysis to determine what variables influence the chance of residual cholesteatoma. There were 42 cases of residual cholesteatoma; 20 in the mesotympanum (including two annular), 17 in the epitympanum, and five in the mastoid. The most important variables for the prognosis of residual disease included age, the state of the stapes, the state of the middle ear mucosa, and the number of sites in the middle ear cleft affected by cholesteatoma. A logistic model was constructed to describe the dependence of the probability of residual cholesteatoma on the two determining variables age and state of the stapes. The implications of these findings for the surgical management of cholesteatoma are discussed.