Mesenteric varices can appear as massive, acute lower gastrointestinal bleeding. The small bowel or colon may be involved, varices usually developing at sites of previous surgery or inflammation in patients with portal hypertension. Two patients with alcoholic cirrhosis and protal hypertension presented with rectal bleeding. Tc-99m RBC studies demonstrated varices and extravasation into the adjacent bowel. The varices were documented by mesenteric angiography. Characteristic features of Tc-99m labeled RBC studies can identify mesenteric varices as the cause of intestinal bleeding and localize the abnormal vessels.