Confusion regarding the diagnosis of Barrett's oesophagus exists because of a false dogma that cardiac mucosa is normally present in the gastro-oesophageal junctional region. Recent data indicate that the only normal epithelia in the oesophagus and proximal stomach are squamous epithelium and gastric oxyntic mucosa. When this fact is recognized, it becomes easy to develop precise histological definitions for the normal state (presence of only squamous and oxyntic mucosa), metaplastic oesophageal columnar epithelium (cardiac mucosa with and without intestinal metaplasia, and oxynto-cardiac mucosa), the gastro-oesophageal junction (the proximal limit of gastric oxyntic mucosa), the oesophagus (that part of the foregut lined by squamous and metaplastic columnar epithelium), reflux disease (the presence of metaplastic columnar epithelium), and Barrett's oesophagus (cardiac mucosa with intestinal metaplasia). It is also possible to assess accurately the severity of reflux which is directly proportional to the amount of metaplastic columnar epithelium, and the risk of adenocarcinoma which is related to the amount of dysplasia in intestinal metaplastic epithelium present within the columnar lined segment of the oesophagus. Histopathological precision cannot be matched by any other modality and can convert the confusion that exists regarding diagnosis of Barrett's oesophagus to complete lucidity in a manner that is simple, accurate, and reproducible.