Primary aorto-colic fistula is rarely reported in the literature. Although infrequently encountered, it is an important complication since it is usually fatal unless detected. Primary aorto-colic fistula is a spontaneous rupture of abdominal aortic aneurysm into the lumen of the adjacent colon loop. Here we report a case of primary aorto-colic fistula in a 54-year old male. The fistulated sigmoid colon was repaired by end-to-end anastomosis. Despite inotropic support, the patient died of sepsis and multiorgan failure on the first postoperative day. (c) 2006 The WJG Press. All rights reserved.