Recently it has been discovered that anomalous union of pancreaticobiliary duct (AUPBD) may play an important role in the pathogenesis of bile duct cancer. Similar to this fact, there were a few reports on the clinical significance of the low junction of the cystic duct (LJCD). LJCD refers to the situation whereby the cystic duct enters the common duct at a low position between the upper margin of the pancreas and the duodenal opening of the bile duct. The pathogenetic mechanism in LJCD is similar to AUPBD in that the pancreatic juice refluxes to the bile duct, mixes with biles, and then generates the mutagens, which act as inflammatory substances and carcinogens on the epithelium of the bile duct. A 51-year-old male who experienced dyspepsia was hospitalized due to his abnormally functioning liver and dilated common bile duct. We confirmed primary cholangiocarcinoma on the common hepatic duct and gallbladder carcinoma associated with LJCD by ERCP and pathologic review of surgical specimen. We report a case of synchronous type double primary cancer associated with LJCD with a brief review of the literatures. (Korean J Gastrointest Endosc 18: 630-636, 1997)