Colonic duplication is a rare congenital anomaly. Generally, two-thirds of cases manifest before the age of 2 years and only a few cases are encountered in adults. The pathogenesis has not yet been confirmed. Morphologically, the condition is divided into two types, cystic and tubular. Treatment is reserved for symptomatic or complicated cases, and surgical resection is the treatment of choice. Prognosis is generally favorable. We report a case of colonic duplicaton in 59-year-old woman. (Korean J Gastrointest Endosc 2007;35:201-204)