Forty-two patients with chronic otitis media underwent preoperative CT scanning followed by surgical exploration of the middle ear and mastoid. The CT finding of abnormal soft tissue density associated with bone erosion was highly correlated with the surgical finding of cholesteatoma. By contrast, the total absence of abnormal soft tissue on CT essentially excluded cholesteatoma. However, 50% of all patients had abnormal soft tissue on CT scan not accompanied by bone erosion. In this largest group of patients it was not possible to diagnose or exclude cholesteatoma on the basis of CT findings alone. Also, CT occasionally gave the erroneous impression of lateral semicircular canal fistulization, tegmen tympani erosion, and facial nerve involvement due to volume averaging of these structures with adjacent soft tissues. CT scan has a role in the evaluation of selected patients with chronic otitis media, but must be interpreted cautiously in view of its limitations and numerous pitfalls.