One hundred and two patients with Crohn's colitis present on average for 8 years, were studied retrospectively in order to determine whether or not a group of patients existed in whom the disease remained limited to the colon, and if such a group could be identified early on in the course of the disorder. At the time of the diagnosis of Crohn's disease, 34 patients had a concomitant anoperineal lesion, while 68 had disease affecting the colon only. In the latter, at the end of the follow-up period, the disease remained exclusively limited to the colon in 39 cases (57 p. cent). The actuarial rate of non-extra-colonic spread was 75, 40 and 35 p. cent at 5, 10 and 15 years respectively. Spread involved above all the anoperineal region (55 p. cent at 10 years), and less often the ileum (20 p. cent at 10 years). In patients monitored for at least 6 years, there was no significant difference between those in whom disease had spread and those in whom it remained limited to the colon, regarding the main initial clinical findings by history and examination, the same applying after the disease had been present for 3 years. These results would go against the existence of a specific entity of "Crohn's disease affecting the colon as an organ" and support the opinion that coloproctectomy with a pouch should be avoided in colitis due to Crohn's disease.