A study of all newly diagnosed patients with gallbladder and biliary tract cancer in Israel during a five-year period indicates that cholelithiasis plays a major part in the ætiology of gallbladder cancer. This conclusion is based on the following findings: (a) high frequency of gallstones in gallbladder cancer cases compared with biliary tract cancer and the general population; (b) similar frequency of gallstones in gallbladder cancer in both sexes and in all ethnic groups; (c) similar sex and ethnic population trends in the incidence of cholelithiasis and of gallbladder cancer.