The diagnosis of primary neoplasm of the gallbladder is a clinical problem the preoperative solution of which may be dependent on a thorough roentgenologic study. Because of the importance of this method of examination, a review of available roentgenograms has been undertaken in a search for possible distinctive and diagnostic characteristics. Films were available in 33 cases seen at the Massachusetts General Hospital in which primary cancer of the gallbladder had been histologically proved. Cases in which the tumor was of undetermined origin were excluded. Carcinoma of the gallbladder is not a common disease, the postmortem incidence being approximately 0.4 per cent (6). At this hospital, over the period covered by the present study, carcinoma of the pancreas was diagnosed four times more frequently than carcinoma of the gallbladder. The gross pathological picture of carcinoma of the gallbladder is conditioned by the anatomy of the organ and of the lymphatic drainage (2, 4). The gallbladder is a subseros...