Primary cystic neoplasms of the intrahepatic and extrahepatic biliary ducts are rare. One biliary cystadenoma and one biliary cystadenocarcinoma have been observed at the UCLA Hospital during the period from 1956 to 1973. Analysis of 31 cases of biliary cystadenoma collected from the world literature reveals the tumor to be slow-growing, with a tendency for malignant alteration. Although most cystadenomas have occurred in the right hepatic lobe of middle-aged women, the only two known cases of cystadenocarcinoma developed in cystadenoma of the left lobe. Hepatic lobectomy for intrahepatic lesions and total excision with biliary diversion for extrahepatic lesions are recommended to avoid recurrence and malignant alteration.