A series of 110 patients with villous tumours of the colon and rectum treated by a single surgeon over an 18-year period is reported. Multiple lesions were present in 15 per cent of patients and 24 per cent of cases contained invasive malignancy, of which 83 per cent were Dukes' A. The major lesion was in the rectum in 84 per cent of patients and in the sigmoid colon in 12 per cent. Rectal bleeding and diarrhoea were the most common presenting symptoms; 6 per cent of patients were asymptomatic. Digital assessment proved a more reliable indicator of the presence of malignancy than either random biopsy or barium enema. In all, 70 of 76 (92 per cent) benign rectal lesions and 15 of 22 (68 per cent) malignant rectal lesions were successfully removed by peranal submucous excision or snaring and none of the malignancies so treated has developed a recurrence to date. Benign recurrence has developed in 13 per cent of all patients; the majority appeared within 4 years and were at the same level as the initial lesion. Of the 79 patients with benign tumours 7.6 per cent have subsequently developed large bowel carcinomas, after 2-16 years; all were symptomatic, half were at the same level as the previous benign lesion, and half were suitable for peranal removal.