The increase in biliary tract surgery and its reported major complications justify a re-evaluation of surgery in this region. Reviews in the literature have shown the necessity of categorizing the diseases and operations of the gallbladder and bile ducts in the evaluation of biliary tract surgery. While the literature has mentioned the importance of coexistent pancreatobiliary diseases, coexistent diseases, coexistent surgery, and the complications of cholecystitis and cholelithiasis in biliary tract surgery, the exact incidence, their relationships, and the importance of these factors on the morbidity and mortality of biliary tract surgery have not been emphasized enough. With these considerations in mind, a comprehensive analysis has been made of 2,285 consecutive operations on the gallbladder and bile ducts performed at Hermann Hospital from 1952 to 1962. The incidence and relationship of the "principal categories" and "coexistent factors" in biliary tract surgery have been tabulated and their importance shown by their