Background: Although it is uncommon, significant bleeding per rectum presents one of the most difficult emergency problems. Bleeding from a rectal ulcer is not well recognized as a cause of such bleeding. Methods: From July 2000 through December 2000, 195 consecutive patients with significant blood loss per rectum were reviewed. Results: Forty-eight cases in whom significant gastrointestinal (GI) bleeding occurred following prior hospitalization were identified. Sources of bleeding were gastroduodenal in 38 cases (79%) and colorectal in 10 cases (21%). The causes of inpatient colorectal bleeding were benign rectal ulcer (n = 4), ischemic colitis (n = 3), neoplasia (n = 2), and diversion colitis (n = 1). Conclusion: The differential diagnosis for inpatients who develop new inpatient GI bleeding differs from that of patients who develop outpatient GI bleeding. Careful examination of the rectum following rectal instrumentation is critical. In addition to the standard resuscitative measures, the identification and treatment of rectal ulcers in this group of patients is of paramount importance. The treatment options for bleeding rectal ulcer include conservative therapy, cauterization, embolization, banding, and local excision.