Giant diverticulum of the colon is a rare complication of the colonic diverticulosis. It generally involves the sigmoid colon. In the chronic form, without symptoms or with only a few non-specific symptoms, an abdominal mass is frequently palpable. A plain abdominal radiogram, showing a gas-filled cyst, can suggest the diagnosis. If needed, an abdominal CT scan is appropriate and seems to be more accurate than a barium enema. The treatment of choice is a segmental resection of the colon involving the giant diverticulum, followed by a direct anastomosis. Despite the old age of these patients, both postoperative morbidity and mortality are low and justify such a radical approach. The acute clinical presentation (about 20%) is generally due to a peritonitis by perforation of the giant diverticulum and requires an emergency colectomy.