We identified 47 patients with nonocclusive ischemia of the large intestine over a seven-year period. The mean age at presentation was 56.2 years, with a 2:2:1 male predominance. Associated medical illnesses were diabetes (17 percent), renal failure (5 percent), and hematologic disorders (5 percent). Six patients developed ischemic colitis after aortic surgery. The mean delay in diagnosis was 1.8 days (range, three hours to 23 days). The right colon was involved in 21 patients (46 percent). Overall, 15 of 16 patients were successfully treated nonoperatively with bowel rest and antibiotics; one patient who was managed nonoperatively died. Among the 31 requiring intestinal resection, enteric continuity was reestablished in 14. Second-look laparotomy in eight patients revealed further ischemia in two (20 percent). Mortality in the operative group was 29 percent (9 of 31). No patient has developed recurrent ischemia (mean follow-up, 5.3 years). Ischemic colitis often occurs without an obvious predisposing event, may involve all segments of the large intestine, and frequently requires surgery. While its course may be self-limited, elderly and diabetic patients, as well as those developing ischemia following aortic surgery or hypotension, continue to have a poor prognosis.