The authors report a case of giant diverticulum of the sigmoid and review the approximately forty cases published in the literature. Clinical manifestations can be either an acute abdominal syndrome of symptoms of a chronic disease. Radiological appearances are usually characteristic: the giant diverticulum is located in the sigmoid, though in one case it arose from the transverse colon. An opaque image was noted in 15 of the patients following barium meal examination, and the lesion was associated with diverticulosis of the colon in every case. Apart from 4 cases, histological appearances were also typical: the colon wall is composed of fibrous tissue which has replaced the normal layers, and the neck of the giant diverticulum is always in the antimesenteric position.