A series of 1578 consecutive colonoscopies performed by radiologists in training is reviewed, with specific reference to patients with colorectal neoplasms. The contribution of the radiologist to the practice of colonoscopy is discussed. This input to the colonoscopy service of a hospital carries several benefits, including the following: a link is established between radiologists and gastroenterologists which improves the standard of both barium enema and colonoscopic examinations; informed discussion is made possible about the suitability of a barium enema lesion for endoscopic removal; the endoscoping radiologist acquires an impartial view of each examination and is able to choose the more appropriate investigation; direct visualisation of the colonic mucosa and its abnormalities may facilitate the interpretation of barium radiographs and enhance the quality of the radiological training that can be offered. In our experience, participation in a weekly colonoscopy session has had no adverse effect on the routine work of the radiology department.