Thirty-nine hospital-based cases of ischemic colitis were reviewed. There were 18 males and 21 females. Average age was 68.7 years (range, 18 to 92 years). Associated diseases among 13 patients younger than 65 included renal failure in seven patients and hematologic, vasculitic, or collagen vascular diseases in four. In 26 patients 65 or older, congestive heart failure was seen in 13, vascular disease in eight, and previous aortic surgery in four. Nineteen patients were treated nonsurgically and 8 died (42 percent mortality). Twenty patients (51 percent) underwent surgery: 18 had resection with colostomy or ileostomy and two had resection with reanastomosis; one patient underwent laparotomy followed by second-look exploration without resection. Thirteen of the 20 surgical patients died (65 percent mortality). Both patients who underwent reanastomosis died of sepsis. The data show a close association between ischemic colitis and a number of serious systemic diseases including renal failure, arteriosclerotic heart and vascular disease, and hematologic, vasculitic, and connective-tissue disease. A predilection for the right colon and sigmoid colon and splenic flexure was seen. A formidable mortality rate (53 percent) was found among patients treated both surgically and nonsurgically.