Although previous gastroscopes have been called gastroduodenoscopes, most endoscopists have had little success in visualizing even the duodenal bulb. We made a new instrument, fiberduodenoscope (made by Machida), in order to observe the duodenum, especially the papilla of Vater. With this fiberduodenoscope it is now possible to regularly view the duodenal bulb and first portion and frequently the second and third portions, including the papilla of Vater. Duodenal ulcer, polyp, diverticulum as well as cancer of the papilla can be diagnosed endoscopically. In addition, we have cannulated the papilla of Vater and injected the pancreatic duct with radio-contrast material.