Details of the study have been reported elsewhere (3 (link), 5 –7 (link),10 (link)–12 (link)). Briefly, primary biliary tract cancer cases (ICD-9 156) diagnosed between 1997 and 2000 were identified through a rapid-reporting system established by the Shanghai Cancer Institute (SCI) with 42 collaborating hospitals in urban Shanghai. This system captured more than 95% of all biliary tract cancers diagnosed in Shanghai. Case patients were permanent residents of urban Shanghai between 40 to 75 years of age. A total of 411 patients with biliary tract cancer (237 gallbladder, 127 bile duct, and 47 ampulla of Vater) were included. In addition, we selected a total of 1,037 biliary stone cases (774 gallstone and 263 bile duct stone patients) from the same hospitals from which the cancer cases were selected. Biliary stone cases had no history of cancer and were matched to index cancer cases on gender, age (within 5 years), and hospital. A total of 959 healthy subjects who were randomly selected from the urban Shanghai population (6.5 million permanent residents), using the Shanghai Resident Registry records, were included in this study as population controls. Controls were free of non-skin cancer and were frequency-matched to cancer cases in a 1-to-1 ratio by age (within 5 years) and gender distributions. All study subjects provided written informed consent. The Institutional Review Boards of the National Cancer Institute and SCI approved the study protocol.