The clinical course of all new patients with ulcerative colitis or indeterminate colitis aged 65 years or older diagnosed in one health district (population 274,000) between 1 January 1975 and 31 December 1984 has been compared with that of all new patients 55 years or younger diagnosed in the same period. Elderly patients were admitted more often in a first attack and were more likely to receive systemic steroids. No elderly patient required urgent surgery and no patient in either group died of ulcerative colitis or its complications. The mortality amongst elderly patients with ulcerative colitis was no greater than expected in a population of the same age. The prognosis for ulcerative colitis in elderly patients is the same as for younger patients.