We report a case of cholecystolithiasis with a rare bile duct anomaly. A 50-year-old man with cholecystolitiasis which was diagnosed at another hospital in June was admitted to the department of medicine in our hospital because of attacks of abdominal colicky pain in September, 1994. Ultrasonogram revealed many stones in the gallbladder, and the patient was referred to the department for operation. Bile duct anomaly was suspected by ERCP. Helical CT following drip infusion cholangiography (DIC) confirmed the biliary distribution using 3-dimensional biliary images (3D-CT). Consequently it was revealed that the cystic duct showed an opening into an accessory bile duct which originated from the common bile duct to the right hepatic duct. Cholecystectomy with resection of the accessory bile duct was performed and a T-tube was placed after choledocholithotomy for a fallen stone in the common bile duct. This bilary anomaly did not belong to any sorts of previously reported classifications, It is important to confirm the biliary distribution to define possible bile duct anomalies to prevent intraoperative injury to the bile duct. Following DIC, helical 3D-CT along with ERCP is very useful for preoperative diagnosis.