Fifteen patients with ischemia of the colon are presented. The majority showed a similar clinical presentation with hematochezia, abdominal pain, and diarrhea in an elderly patient population having associated disease. Colonoscopy was abnormal in all patients studied. Three endoscopic stages were recognized; (1) acute stage characterized by petechiae, pallor, and hyperemia; (2) subacute stage consisting of ulceration and exudation; and (3) chronic stage characterized by stricture, decrease in haustrations, and mucosal granularity. Conventional barium enemas were abnormal and suggested ischemic colitis in six of 15 patients. Rigid proctoscopy was normal or demonstrated nonspecific proctitis in 12 of 15 patients studied. Colonoscopic biopsies demonstrated superficial inflammatory changes in all patients. Thirteen patients had complete mucosal healing endoscopically in 2 weeks to 3 months with stricture developing in four patients. Because ischemic colitis is a distinct subtype of ischemic bowel disease most often limited to the superficial mucosa, colonoscopy is an alternative and usually safe modality in the diagnosis of this entity and proved more accurate that conventional x-ray and proctoscopy.