Over a 28-month period, 100 transanal endoscopic microsurgical excisions of rectal tumours were carried out in three centres. The histological diagnosis was benign adenoma in 77 and invasive adenocarcinoma in 23. Complete excision of the tumour with histological confirmation was achieved in 70 (91 per cent) of the adenomas and in all but one of the carcinomas. Of the carcinomas, 18 were recognized before operation and the remaining five were diagnosed on postoperative histology. Of the patients with carcinoma, one had immediate further surgery, nine had radiotherapy and 13 had no extra treatment. To date, four patients have had a recurrence of villous adenoma, and two of the patients treated for invasive carcinoma have had local recurrence. These initial results of transanal endoscopic microsurgery in the UK compare well with those of earlier reports, indicating that the technique has a useful place in the management of sessile adenomas of the mid and upper third of the rectum, and of some carefully selected carcinomas.