The clinical and radiological findings of 12 patients with early carcinoma of the ampulla or papilla of Vater are described. Endoscopic retrograde cholangio-pancreatography, percutaneous transhepatic cholangiography and hypotonic duodenography are the radiological techniques most suited to making the diagnosis. An irregularly bordered obstruction in the ampulla or papilla is characteristic of carcinoma. The presence of an inflamed, rounded or prolapsed papilla or delayed efflux of contrast from the bile and pancreatic ducts and local inflammatory changes in the head of the pancreas are indirect signs of a tumour in this region.