Objective: To evaluate the radiographic characteristics of the ampulla of Vater cancer. Subjects and Methods:The authors analyzed retrospectively the US(n=25) and CT(n=15) findings in 25 cases of ampulla of Vater cancer, with emphasis on the potential of CT & US in regand to the detectibility of the mass. ERCP(n=15) and hypotonic duodenography(n=5) were also evaluated for the configuration of obstructed duct. RESULTS: The tumor was detected on sonography in only 12 cases(48%) as a small, relatively well delinated mass with slighty low echogenicity to the pancreas. The tumor was shown by CT in 8 cases(53% ) as a well delinated mass protruding into the second portion of duodenal lumen with slightly low attenuation to the pancreas. CBD was dilated in 25 cases(100%), but pancreatic duct was dilated in 15 cases(60%). Obstructed end of CBD was nipple shaped in 7 cases(47%), clubbed in 3, flat in 3, and indistict in 2 by ERCP. Hypotonic duodenogram showed irregular filling defect in the medial wall of second portion of the duodenum in 5 cases (100%). CONCLUSION: Mas detection rate crsing US or CT were not high in ampulla of Vater cancer. Except for a CT finding of a small mass protruding into the regional duodenal lumen, other finclings were nonspecific. Therefore, additional studies or more afgressive approach should be attempted for a correct diagnosis.