An acute hemorrhagic rectal ulcer (AHRU) is considered to be a potentially life-threatening illness requiring urgent identification and management because of massive bleeding. It is therefore important to clarify the factors associated with the massive bleeding of an AHRU and the best management. The factors associated with the massive bleeding of 14 patients with AHRU were determined by comparing the clinicopathologic features, laboratory data, and treatment between four patients with more transfusions (> or = 12 U) and 10 patients with less transfusions (< or = 3 U). Patients with AHRU of the more transfusion group had lower performance status (PS), more diabetes mellitus, more comorbid diseases, and lower serum albumin concentrate than those of the less transfusion group. More surgical treatment and the administration of hemostatic agents were necessary for the patients with AHRU of the more transfusion group than for those of the less transfusion group, and the duration from bleeding to hemostasis in patients with AHRU of the more transfusion group was larger than that of the less transfusion group. Patients with AHRU of the more transfusion group had a longer duration of no oral food intake, total parenteral nutrition, and hospital stay from bleeding day than those of the less transfusion group. Thus, the factors associated with the massive bleeding of AHRU were identified.