Multiple synchronous tumors of the extrahepatic biliary tree are not frequently reported. Over a 2-year period, 54 operative procedures were performed for tumors of the extrahepatic biliary tract or periampullary region. In five of these cases, unsuspected tumors were observed. Of these, one patient had multiple benign papillomatosis of the extrahepatic biliary tree. All four of the other patients were found to have unsuspected small carcinomas of the gallbladder in association with mid- or low bile duct cancer. Multiple tumors of the extrahepatic biliary apparatus may occur more frequently than previously thought, and the incidence of unsuspected gallbladder cancer in association with bile duct cancer may be high. These tumors should be suspected and looked for in each instance by intraoperative endoscopy and careful histologic examination of the gallbladder.