This article reviews the epidemiology, clinical manifestations, diagnosis, prognosis, and treatment of inflammatory bowel disease (IBD), which will grow in prevalence as the population ages. Prognosis of late-onset ulcerative colitis (UC) is generally similar to that of early-onset UC, whereas in Crohn disease it is probably better because of a tendency for colonic involvement. Disease complications are related more to the duration of the inflammatory bowel disease than the subject's current age. The diagnosis in elderly patients can be challenging due to the large number of conditions that mimic IBD on radiologic, endoscopic, and histologic testing. Distinguishing these conditions from IBD will significantly alter prognosis and treatment. Complications related to IBD and its treatment are common and must be recognized early to limit their impact in a vulnerable elderly population.