The value of gastroduodenal endoscopy and retrograde cholangiopancreatography has been assessed in 55 patients subsequently confirmed to have pancreatic carcinoma. The technique provided a precise and accurate diagnosis in 45 patients. In nine of these patients, the diagnosis was obtained by duodenoscopy and biopsy alone. Cannulation of the duct was attempted in 47 of the 55 patients; roentgenograms of the pancreatic or biliary tree, or both, were obtained in 40 studies, 36 of which were diagnostic. Tumors were most common in the head of the pancreas, and virtually all roentgenograms showed duct obstruction or a major stricture with upstream dilatation. One pancreatogram of poor quality was reported as normal. Endoscopic cholangiograms were often diagnostic when pancreatography failed in patients with tumors of the head of the pancreas. Endoscopic retrograde cholangiopancreatography is a precise technique for the diagnosis of patients with tumors of the papilla of Vater which may present relatively early and prove resectable. Patients with tumors of the pancreas itself usually present with advanced disease, and in this series, endoscopic retrograde cholangiopancreatography provided no clear benefit in terms of operability or patient survival. However, the efficient documentation of inoperable tumors is important, and endoscopic retrograde cholangiopancreatography sets a standard against which other techniques can be evaluated.