Carcinoid tumours of the rectum are very rare, and they may present special therapeutic problems for the surgeon. Tumour size and muscle layer invasion are the two most important factors predicting their malignant potential. A series of 20 patients with carcinoid tumours of the rectum were reviewed. 16 tumours less than 2 cm in diameter had neither muscle layer invasion nor lymph node metastases, with the exception of one tumour. Four patients with tumours larger than 2 cm died from metastatic carcinoid. In order to plan operative management endoluminal ultrasound should be performed preoperatively. Rectal carcinoid tumours should be treated like carcinomas of the rectum if they are 2 cm or more in diameter or if they demonstrate muscularis propria invasion independent of tumour size.