This paper reports the radiographic findings in 84 cases of biopsy-proven pancreatic and biliary malignancies studied by endoscopic retrograde cholangiopancreatography. In the 73 successful studies a diagnosis of tumor could be made in 67 patients (92%). The study was successful in 40 of 43 patients with pancreatic carcinoma and the diagnosis could be made in 37 on the basis of stenosis or obstruction of the ducts. There were 33 successful studies in the 41 patients with miscellaneous tumors including primary bile duct, ampullary, gallbladder, metastatic carcinoma, lymphoma, and hepatoma. A diagnosis of tumor was made in 30 studies. As has been observed in carcinoma of other hollow structures, the hallmark of malignancy in the pancreatic and biliary tract is obstruction and stenosis. This study indicates that malignant disease of the pancreas and tract is accurately assessed by this endoscopic method.