This chapter provides detail description of Hiatus hernia and gastroesophageal reflux disease (GERD). Chapter has 28 well illustrated diagrams and pictures. Hiatus hernia, Sliding hiatus hernia, gastric mucosal prolapse, gastroesophageal reflux disease, esophagitis, concomitant peptic ulcer, diaphragmatic indentation, bell like appearance, squamo-columar junction, Lax LES, Sarvay-Miller grading, linear erosion, linear ulcer, GERD, Roux-en-Y conversion, peptic stricture, Barrett\'s esophagus are described in detail with the help of coloured pictures and relevant text given in boxes. One flow chart is included to highlight surveillance protocol for Barrett\'s esophagus by American college of gastroenterology.