Colonic ischemia is the most prevalent form of gastrointestinal ischemia and causes 3∼ 9% of all acute lower intestinal bleeding. Most common cause is known to be cardiac embolus. A 67-year-old female patient presented with rectal bleeding. The patient had cerebral infarction 15 days ago. A colonoscopy showed a large ulcer with hemorrhage in the rectum. Computed tomography showed deep vein thrombosis from the left popliteal vein to infrarenal inferior vena cava. Transthoracic echocardiography was carried out, but no abnormal feature was found. Then, tran sesophageal echocardiography, with agitated saline contrast to find out a right to left shunt, was performed, patent foramen ovale was found. This patient was treated with anticoagulation and inferior vena cava filtering. We suggest this ischemic colitis may be due to arterial embolization from deep vein thrombosis through PFO. (Korean J Gastrointest Endosc 2004;28:208212