A double or bilobed gallbladder is a rare congenital anomaly, occurring at a rate of 1/4,000∼5,000. We encountered a case of a double gallbladder that was diagnosed by an endoscopic retrograde cholangiogram. In view of the paucity of this anomaly, we report the case of a patient with a double gallbladder (Y duplication) accompanied by a common bile duct (CBD) stone. We also discuss the characteristics, classification, embryology and treatment of the double gallbladder. (Korean J Gastrointest Endosc 2007;35:369-372)