Cathartic colon is not rare. Heilbrun reported 9 cases. We have seen 6 cases during the last 2 years. In 3 of these patients, a diagnosis of ulcerative colitis was made. Although a definite differential diagnosis from ulcerative colitis may be impossible on roentgen study, the changes described above should alert the radiologist to the possibility of cathartic colon. The history is characteristic: the ingestion for many years of drastic, irritant cathartics that have their action primarily on the colon.