The unique characteristics of the toposcopic catheter have suggested its application in the gastrointestinal system. The operation of the catheter promises to facilitate the catherterization of the pancreatobiliary ducts through the Papilla of Vater. An initial series of patients has undergone routine endoscopic retrograde cholanopancreatography (ERCP) using the topocatheter for contrast infusion. An extensively modified topocatheter is passed through an appropriately positioned endoscope. The catheter tip is placed within the ampulla, and the toposcopic element is everted. In basic ERCP, contract medium is then injected for appropriate diagnostic procedures. In addition, the topocatheter's ability to atraumatically negotiate small, tortuous ducts, is being applied to catheterization of remote pancreatic ducts for sampling of pure secretions, and of the cystic duct, for sampling and possible infusions for dissolution of gall stones.