Eight patients over age 60 years had sudden onset of acute abdominal pain and rectal bleeding in the absence of prior inflammatory bowel disease. Several improved on medical therapy alone; those who required surgery suffered no recurrence up to 6 years. Although the pathologic specimens on these patients were first considered to represent ulcerative colitis or Crohn's disease, their histories and clinical courses are much more consistent with ischemic colitis. Since there are only a limited number of reactions that the bowel can muster against a host of damaging processes, histologic criteria alone are usually not sufficient to separate ischemic disease of the colon from ulcerative colitis and Crohn's disease. This is also true of radiographic features. Thus the diagnosis of ischemic colitis rests on clinical onset and course after treatment.