In order to determine whether abdominopelvic computed tomography (CT) offers an alternative to barium enema (BE) for the investigation of the large bowel in frail elderly patients, we have assessed and compared the results of both tests performed in each patient. Thirty-seven patients aged 71 to 88 (mean 80) with a history or clinical findings suggestive of large bowel disease were studied. The seven colonic neoplasms in this group were demonstrated by both techniques (apart from one patient who did not undergo BE as CT had shown an obstructing lesion). CT showed useful additional data in four patients (e.g. abdominal wall involvement) and demonstrated numerous extracolonic lesions (e.g. ovarian carcinoma). However, CT did raise the possibility of a large bowel neoplasm in four patients where none was shown by BE and missed one case of Crohn's disease. CT was the preferred test amongst the 25 patients where the acceptability of the two techniques could be compared. Only in 16 patients were the BE studies adjudged to be of good quality. CT should be the initial investigation of the large bowel in frail elderly patients requiring inpatient bowel preparation; the more unpleasant BE could be reserved for those cases where CT is equivocal or severe symptoms are unexplained.