The study comprises 16 patients who during the period 1965-1972 underwent mucosal denudation (stripping) for multiple, highly differentiated, non-invasive bladder papillomas. No major complications to the operation were seen. In 3 of the 16 patients histological examination of the operative specimen revealed a more malignant tumour than found on preoperative biopsy. During the observation period, which averaged 4 years, the disease recurred in 10 of the 16 patients. In 4 of them, repeated biopsy showed a more malignant tumour than did the operative specimen. The study moreover demonstrated that following mucosal stripping, pronounced bladder contracture occurred in all the patients and dilatation of the upper urinary tracts in half of them. These serious complications mean that even if the disease does not recur, a reasonably normal life for the patient is unattainable. The method, consequently, cannot be recommended.