In the United States over 450,000 participants finished a marathon in 2002. Some of them will present to an Emergency Department (ED) with a variety of gastrointestinal complaints. The diagnosis of ischemic colitis should be considered in patients who present with bloody diarrhea. We describe three patients who presented to our ED with abdominal pain and bloody diarrhea after a marathon. Gastrointestinal complaints with emphasis on mesenteric ischemia and ischemic colitis are discussed.