Objective: The objective of the study was to investigate bleeding (LGIB) in patients with acquired immunodeficiency syndrome (AIDS). Methods: All hospitalized AIDS patients with LGIB evaluated by the gastroenterology service at a large city-county hospital during a 6 yr period were identified by database review and by endoscopy and consultation records. Results: Of the 691 AIDS patients seen during the study period, 18 (2.6%) (median age 41 ± 7 years) were evaluated for LGIB. In these patients, LGIB was caused by human immunodeficiency virus type 1 (HIV)-associated disorders in 72% including cytomegalovirus colitis in seven patients, idiopathic colonic ulcers in five patients, and intestinal Kaposi's sarcoma in one patient. HIV-associated thrombocytopenia contributed to substantial bleeding from hemorrhoidal disease in two patients. Rebleeding occurred in four patients (22%), including hemorrhoids in three and idiopathic colonic ulcers in one. Surgery was not performed in any patient. Following the institution of ganciclovir therapy, no patient with CMV colitis had recurrent bleeding. The in-hospital mortality was high (28%), although bleeding was the direct cause of death in only one patient. Conclusions: LGIB is infrequent in patients with AIDS and is usually caused by opportunistic diseases specifically related to immunodeficiency. Although some of these conditions are potentially treatable medically, in-hospital mortality is high and long-term prognosis is poor because of AIDS-related comorbidity.