A review was made of 150 cases of chronic otitis media caused by cholesteatoma that were operated consecutively; no complications or active otorrhea was present. In 61.3% of cases, prophylactic antibiotic (PA) treatment was given on the basis of the surgeon's criteria, which probably reflected the presence or absence of risk factors. Most patients were given a penicillin or penicillin derivative (amoxi-ampicillin followed by cephalosporins). Antibiotic administration was prolonged longer than necessary (mean 3.4 days). PA was not associated with important complications. Postoperative infection occurred in 10.7% of cases, usually infection of the surgical wound, most commonly by Staphylococcus aureus. Otorrhea occurred in 7.3% of cases in the 15 days after surgery and was more frequent in patients treated via an endomeatal approach and in those who had ossicular prosthesis. Prophylactic antibiotic treatment produced no benefit to our patients in the form of any reduction in number of surgical infections, postoperative otorrhea or mean hospital stay. Therefore, PA is not recommended in surgery for uncomplicated cholesteatoma. When risk factors are present, a suitable and complete antibiotic treatment may be indicated.