Gastro – intestinal duplications are usually detected in children before 2 years of age due symptoms/complications associated with the condition or during surgery in the child for some unrelated condition. In adults colonic duplication is of rare occurrence and often diagnosed during surgery. However, it may be diagnosed pre operatively due to symptoms of obstruction, volvulus or rarely due to perforation. We present an adult having tubular duplication of ascending colon, that presented with perforation. The duplication had a blind end and did not have distal communication. In addition, it had its own blood supply. The management of the case is discussed. Aetiogenesis of the anomaly is enumerated and literature reviewed. For ascending colon duplication similar meaning word accessory ascending colon has also been used in the manuscript.