This chapter provides detail description of Chronic duodenal ulcer. Chapter has 40 well illustrated diagrams and pictures. Duodenitis, deformed duodenal bulb, Brunner’s gland hyperplasia, duodenal ulcer, choledochoduodenal fistula, kissing ulcers, giant kissing ulcer, complications of duodenal ulcer, endoscopic stigmata of ulcer bleeding, actively oozing ulcer, duodenal stenosis are described in detail with the help of coloured pictures and relevant text given in boxes.