Large colonic villous adenomas are benign neoplasms capable of malignant transformation with a higher frequency than other adenomas. Such transformation often requires surgical therapy after endoscopic resection. The aim of the present study was to establish the indications for surgery in a series of 13 cases of large colonic villous adenomas initially submitted to endoscopic resection. The patients (8 males and 5 females; mean age; 62 years) were observed over the period 1993-2000. All endoscopic resections were performed using the piecemeal technique. In 7 cases there were 2 endoscopic sessions and in one case 3; a single case of post-endoscopic bleeding was treated conservatively. In 5 cases, endoscopic resection was deemed not to be radical and these patients were submitted to surgical resection. Histology on the surgical specimens revealed 2 cases of carcinoma (T1 and T2, respectively), confirmation of colonic villous adenoma in 2 cases and the presence of inflammatory tissue in 1 case. Among the patients treated with endoscopic resection alone one death occurred at two years due to lung and systemic metastases probably due to the malignant adenoma. After a review of the literature and on the basis of their own experience, the authors stress the importance of a combined pathological and endoscopic approach to establish when surgery is required.